Recombinant Mycoplasma pneumoniae GTPase obg (obg)

What distinguishes Obg GTPase from other bacterial GTPases?

Obg GTPases possess unique biochemical properties that clearly differentiate them from Ras-like GTPases. They display slow rates of GTP hydrolysis with micromolar binding constants for both GTP and GDP. Unlike Ras GTPases, Obg proteins exhibit rapid dissociation constants for GTP and GDP that are 10³-10⁵ times faster. Most notably, Obg functions independently of GTPase activating proteins (GAPs), guanine nucleotide exchange factors (GEFs), and guanidine dissociation inhibitors (GDIs) . These distinctive properties suggest that Obg proteins act as intracellular sensors with their nucleotide-bound state controlled primarily by the relative GTP/GDP concentration within the cell .

The conserved GTPase domain contains the signature G1-G5 motifs essential for GTP binding and hydrolysis:

• G1 [GxxxxGKS/T]: P-loop/Walker A motif

• G2 [T]: Switch I region

• G3 [DxxG]: Switch II/Walker B motif

• G4 [(N/T)(K/Q)xD]: Guanine base recognition

• G5 [SA(K/L)]: Less conserved motif for guanine recognition

Why is Obg GTPase considered essential in bacterial physiology?

Obg homologs are essential for the survival of both Gram-positive and Gram-negative bacteria, making them universal bacterial proteins. Studies have confirmed their essentiality in numerous species including Bacillus subtilis, Streptococcus pneumoniae, Staphylococcus aureus, Haemophilus influenzae, Escherichia coli, Vibrio harveyi, and Vibrio cholerae . In Mycoplasma pneumoniae, which already has a minimal genome, Obg remains indispensable for cellular viability.

The essentiality of Obg stems from its critical roles in:

• Ribosome biogenesis: Obg acts as an rRNA chaperone by recruiting ribosomal proteins and assembly factors to the assembly pathway .

• Quality control mechanisms: Ensures that only mature subunits assemble into functional ribosomes .

• Stress response regulation: Enables bacterial adaptation to changing environmental conditions.

• Cell division processes: In some bacteria, Obg is implicated in regulating cell division.

This multifunctional nature and universal essentiality make Obg an attractive target for broad-spectrum antimicrobial development.

How does the structure of Obg relate to its function?

Obg proteins typically consist of three main domains with distinct functions:

In ribosome assembly, Obg's structure enables it to function as a molecular checkpoint, preventing premature association of immature ribosomal subunits. The protein's ability to sense the GTP/GDP ratio couples ribosome assembly with cellular energy status and growth control pathways.

What approaches can be used for recombinant expression and purification of M. pneumoniae Obg?

Successful expression and purification of recombinant M. pneumoniae Obg can be achieved through the following optimized protocol:

• Expression system:

  • E. coli BL21(DE3) strain is commonly used due to its reduced protease activity

  • Expression vector: pET series vectors (e.g., pET-28a) with C-terminal 6×His tag

• Cloning strategy:

  • PCR amplification of the obg gene from M. pneumoniae genomic DNA

  • Restriction enzyme digestion (typically NcoI and HindIII as demonstrated for other Obg proteins)

  • Ligation into expression vector and transformation into E. coli

• Expression conditions:

  • Induction with 0.5-1 mM IPTG at OD600 ~0.6

  • Expression at lower temperatures (16-25°C) for 12-18 hours improves solubility

• Purification procedure:

  • Cell lysis in buffer containing 50 mM Tris-HCl pH 8.0, 500 mM NaCl, 5 mM imidazole, and protease inhibitors

  • Immobilized metal affinity chromatography (IMAC) using Ni-NTA resin

  • Elution with imidazole gradient (20-500 mM)

  • Optional ion exchange chromatography for higher purity

  • Size exclusion chromatography as final polishing step

• Quality control:

  • SDS-PAGE for purity assessment (>95% purity desired)

  • Western blot confirmation

  • Functional testing via GTPase activity assay

Including 5 mM MgCl₂ and 1 mM DTT in all buffers helps maintain protein stability and activity throughout the purification process.

How can GTPase activity of Obg be measured and what controls are necessary?

Several complementary approaches can be employed to measure Obg GTPase activity:

• Colorimetric phosphate detection assays:

  • BIOMOL Green assay: Measures inorganic phosphate released during GTP hydrolysis

  • Typical reaction conditions: 20-50 μM Obg, 100-200 μM GTP, 37°C

  • This assay can be adapted to 384-well format for high-throughput screening with Z' values of approximately 0.58±0.02

• Fluorescence-based assays:

  • Utilizing mant-GTP and mant-GDP (N-methyl-3'-O-anthranoyl-guanine nucleotides)

  • Fluorescence increases upon binding to Obg (excitation ~355 nm, emission ~448 nm)

  • Can measure both binding kinetics and GTPase activity

• Essential controls:

  • Negative control: Reaction buffer without Obg protein

  • Positive control: Well-characterized GTPase with known activity

  • Obg variant with mutations in G-domains: A variant of Obg with multiple alterations in the G-domains that prevent nucleotide binding serves as an excellent negative control

When screening for potential inhibitors, compounds resulting in ≥15% reduction in activity should be selected for repeat screening, with those demonstrating ≥50% inhibition advancing to dose-dependence studies .

What methodological considerations are important when designing nucleotide binding studies?

When studying nucleotide binding to Obg GTPase, several methodological considerations are crucial:

• Choice of nucleotide analogs:

  • Mant-labeled nucleotides (mant-GTP, mant-GDP) provide sensitive detection of binding events

  • Fluorescent properties: Increased fluorescence upon protein binding

  • Concentration range: Typically 0.5-5 μM for binding studies

• Buffer composition:

  • Magnesium is critical: 5-10 mM MgCl₂ should be included

  • Physiological salt concentration: 100-150 mM NaCl

  • Optimal pH: 7.5-8.0 (typically Tris-HCl or HEPES buffer)

  • Reducing agents: 1 mM DTT to maintain cysteine residues

• Data collection parameters:

  • Temperature control: Maintain consistent temperature (typically 25°C)

  • Equilibration time: Allow sufficient time for binding equilibrium (5-15 minutes)

  • Fluorescence settings: Excitation at 355 nm, emission at 448 nm

• Control experiments:

  • Protein-free control to account for background fluorescence

  • Engineered Obg variant (ΔObg) with mutations in G-domains that prevent nucleotide binding as negative control

  • Competition experiments with unlabeled nucleotides to verify specificity

• Data analysis:

  • Binding curves fitted to appropriate models (typically single-site binding)

  • Determination of dissociation constants (Kd)

  • Comparison between GTP and GDP binding parameters

These considerations ensure reliable and reproducible nucleotide binding data that can inform structure-function relationships and inhibitor development efforts.

How can site-directed mutagenesis be applied to study Obg function?

Site-directed mutagenesis offers powerful insights into structure-function relationships of Obg:

• Key targets for mutagenesis:

  • G-domain motifs (G1-G5): Mutations in conserved residues disrupt GTP binding or hydrolysis

  • Switch regions: Affect conformational changes upon nucleotide binding

  • RNA or protein interaction domains: Identify residues essential for partner binding

• Design of a nucleotide-binding deficient variant:

  • Multiple alterations in G-domains create variants unable to bind nucleotides

  • For example, the ΔObg variant can be constructed through gBlock fragment technology with mutations in key G-domain residues

  • This variant serves as an excellent control in binding and activity assays

• Methodological approach:

  • PCR-based mutagenesis using complementary primers containing desired mutations

  • Confirmation by DNA sequencing

  • Expression and purification as for wild-type protein

  • Functional characterization using activity and binding assays

• Validation methods:

  • Fluorescent nucleotide binding assays with mant-GTP/GDP to confirm binding defects

  • GTPase activity measurements to assess catalytic function

  • Structural analysis by circular dichroism to verify proper folding

Through strategic mutations, researchers can dissect the roles of specific residues and domains in Obg function, providing valuable insights for inhibitor development and understanding bacterial physiology.

What is the role of Obg in ribosome assembly and bacterial stress response?

Obg plays critical roles in both ribosome assembly and stress response, functioning as a molecular connector between these essential processes:

• Ribosome assembly functions:

  • Acts as an rRNA chaperone by recruiting proteins and assembly factors to the ribosome assembly pathway

  • Establishes quality control mechanisms ensuring only mature subunits assemble into functional ribosomes

  • Particularly important in late-stage maturation of the large ribosomal subunit (50S in bacteria, mtLSU in mitochondria)

  • Functions as an anti-association factor preventing premature subunit joining

• Stress response regulation:

  • Senses GTP/GDP ratios as an indicator of cellular energy status

  • Couples ribosome assembly with growth control pathways

  • May interact with stringent response components

  • Required for adaptation to nutrient limitation and temperature stress

• Integration of functions:

  • The loss of ribosome assembly GTPases abolishes ribosome formation and leads to translation deficiency

  • This creates a checkpoint mechanism linking environmental stress to protein synthesis capacity

  • Enables bacterial adaptation to changing conditions in host environments

These dual roles make Obg essential for bacterial survival under diverse conditions, including those encountered during infection.

How do peripheral tolerance mechanisms relate to Obg function in bacterial systems?

While not directly related to Obg function, understanding peripheral tolerance mechanisms provides insights into how bacterial proteins like Obg may interact with host immune systems:

• Parallel regulatory mechanisms:

  • Peripheral tolerance involves tightly regulated T-cell responses to antigens

  • Similarly, Obg regulates bacterial responses to environmental stressors

  • Both systems employ sophisticated checkpoint mechanisms

• Potential interactions during infection:

  • Bacterial Obg may influence expression of immunomodulatory factors

  • These factors could potentially affect host T-cell responses

  • Understanding such interactions could inform vaccine development strategies

• Experimental approaches for investigating potential relationships:

  • Co-culture systems with immune cells and bacteria with modified Obg expression

  • Analysis of immune responses to bacterial antigens under conditions affecting Obg function

  • Proteomics approaches to identify Obg-regulated immunomodulatory factors

Although direct evidence linking Obg to peripheral tolerance mechanisms is limited, exploring potential connections could yield new insights into host-pathogen interactions.

How does Obg contribute to Mycoplasma pneumoniae pathogenesis?

The role of Obg in M. pneumoniae pathogenesis remains an area of active investigation, with several potential mechanisms:

• Essential role in bacterial viability:

  • As an essential protein, Obg is required for M. pneumoniae survival during infection

  • This makes it a promising antimicrobial target

• Potential connections to virulence mechanisms:

  • M. pneumoniae contains repetitive elements (RepMPs) involved in sequence variation in adhesin P1 and adherence-related protein B/C

  • While direct connections to Obg remain unexplored, Obg's role in stress response could influence expression of these elements

  • RepMP-mediated recombination events could affect bacterial survival in the respiratory tract

• Stress adaptation in host environments:

  • Obg's function in stress response likely helps M. pneumoniae adapt to the human respiratory tract

  • This adaptation is critical for establishing and maintaining infection

• Potential role in chronic infection:

  • Long-term bacterial persistence requires sophisticated stress response mechanisms

  • Obg may contribute to the ability of M. pneumoniae to establish chronic infections

Future studies specifically examining Obg function during infection will provide more definitive insights into its role in pathogenesis.

How can genomic engineering approaches be applied to study Obg function in vivo?

Several genomic engineering technologies can provide valuable insights into Obg function in Mycoplasma pneumoniae:

• Recombinase-assisted genomic engineering (RAGE):

  • This technology has been developed specifically for editing the M. pneumoniae genome

  • The approach uses landing pads consisting of antibiotic resistance markers flanked by incompatible lox sites

  • These landing pads can be inserted in targeted locations by homologous recombination mediated by the GP35 recombinase

  • For studying Obg, a landing pad could be inserted near the obg gene to facilitate conditional expression or tagging

• Cre recombinase-mediated cassette exchange (RMCE):

  • Allows exchange of genetic material at specific locations

  • Can be used to introduce modified versions of obg to study structure-function relationships

  • Methodology employs incompatible lox sites (e.g., lox71 and loxm2/66) to ensure directional exchange

• Practical implementation for Obg studies:

  • Construction of landing pads near regulatory regions of obg

  • Amplification of landing pad cassettes with phosphorylated/protected oligonucleotides

  • Isolation of single-stranded DNA by lambda exonuclease treatment

  • Electroporation of ssDNA into M. pneumoniae containing the GP35 recombinase

  • Selection based on antibiotic resistance

  • Confirmation by PCR using specific oligonucleotides

These approaches enable sophisticated genetic manipulation of M. pneumoniae to study Obg function in its native context.

What high-throughput screening approaches are most effective for identifying Obg inhibitors?

A validated high-throughput screening cascade has been developed specifically for identifying Obg inhibitors:

• Primary GTPase activity screening:

  • 384-well format colorimetric assay using BIOMOL Green

  • Reaction components: Purified Obg protein, GTP, and test compounds

  • Measures inhibition of phosphate release during GTP hydrolysis

  • Validated with Z' values of approximately 0.58±0.02, indicating a robust assay suitable for high-throughput screening

  • Successfully used to screen libraries of 40,000+ compounds

• Hit selection criteria:

  • Compounds resulting in ≥15% reduction in Obg activity selected for repeat screening

  • Follow-up testing performed in triplicate

  • Compounds demonstrating ≥50% inhibition selected for dose-dependence studies

• Secondary validation assays:

  • Fluorescence-based binding assays using mant-GTP and mant-GDP

  • Competition assays to determine mechanism of inhibition

  • Counter-screening against control GTPases to assess selectivity

• Broad-spectrum potential assessment:

  • Testing activity against Obg proteins from multiple bacterial species

  • Recombinant Obg proteins from pathogens such as Klebsiella pneumoniae (Obg KP) and methicillin-resistant Staphylococcus aureus (Obg MRSA) can be used

  • Confirms potential for broad-spectrum antimicrobial development

This systematic approach enables efficient identification of promising Obg inhibitors with potential broad-spectrum activity.

How can rapid diagnostic assays for M. pneumoniae be optimized using knowledge of conserved genes like obg?

Knowledge of highly conserved genes like obg can inform the development of improved diagnostic assays for M. pneumoniae:

• Recombinase-aided amplification (RAA) technology:

  • RAA provides rapid isothermal amplification of target sequences

  • The P1 gene has been successfully targeted for M. pneumoniae detection

  • Conservative genes like obg could provide alternative targets with high specificity

• Target selection considerations:

  • Conserved regions within the obg gene ensure consistent detection across strains

  • Primer-BLAST can be used to confirm specificity of designed primers and probes

  • Online OligoEvaluator software can analyze potential for primer dimers and hairpins

• Assay optimization parameters:

  • Analytical sensitivity: RAA assays targeting conserved genes can achieve detection limits as low as 2.23 copies per reaction

  • This represents approximately 19.4 fg of DNA, significantly more sensitive than real-time PCR (194 fg)

  • Reaction conditions: Isothermal amplification at 39-42°C for 15-30 minutes

• Validation methodology:

  • Testing with plasmid standards containing target gene fragments

  • Serial dilutions from 10⁴ to 10⁰ copies per reaction

  • Statistical analysis using probit analysis to determine detection limits

  • Comparison with reference methods such as commercial real-time PCR

Targeting highly conserved genes like obg could enhance both sensitivity and specificity of molecular diagnostic assays for M. pneumoniae.

What structural biology approaches can provide insights into Obg function and inhibitor development?

Advanced structural biology techniques can illuminate Obg function and accelerate inhibitor development:

These complementary approaches can provide comprehensive structural insights, guiding rational design of selective Obg inhibitors while elucidating fundamental mechanisms of Obg function.

Why is Obg considered a promising broad-spectrum antibiotic target?

Obg possesses several characteristics that make it an exceptional target for antimicrobial development:

• Essential nature:

  • Obg is required for survival across diverse bacterial species

  • Essential in both Gram-positive and Gram-negative bacteria, including Bacillus subtilis, Streptomyces coelicolor, Staphylococcus pneumoniae, S. aureus, Haemophilus influenzae, Escherichia coli, Vibrio harveyi, and Vibrio cholerae

  • No known bypass mechanisms exist

• High conservation:

  • Obg is one of the most highly conserved bacterial GTPases

  • Present in virtually all bacteria, including multidrug-resistant pathogens

  • The conserved GTPase domain provides a universal targeting site

• Unique biochemical properties:

  • Distinct from human GTPases in several key aspects

  • Slow GTP hydrolysis rate and micromolar binding constants

  • Rapid nucleotide dissociation constants

  • These differences allow for selective targeting

• Multifunctional roles:

  • Involved in essential processes including ribosome assembly and stress response

  • Targeting Obg affects multiple cellular pathways simultaneously

  • This multifaceted impact reduces the likelihood of resistance development

These attributes make Obg an ideal candidate for the development of novel broad-spectrum antibiotics to address the growing crisis of antimicrobial resistance.

What are the challenges in developing selective inhibitors of bacterial Obg?

Despite Obg's promise as an antimicrobial target, several significant challenges must be addressed:

• Compound penetration barriers:

  • Bacterial cell wall/membrane penetration, particularly in Gram-negative bacteria

  • Efflux pump evasion to maintain intracellular concentration

  • Special considerations for Mycoplasma, which lacks a cell wall but has a complex membrane

• Biochemical challenges:

  • Low intrinsic GTPase activity complicates assay development and hit validation

  • High intracellular GTP concentrations (1-2 mM) may compete with inhibitors

  • Need for compounds that can overcome physiological nucleotide concentrations

• Selectivity requirements:

  • Distinguishing bacterial Obg from human homologs to minimize side effects

  • Maintaining activity across bacterial species while limiting effects on host cells

  • Balancing broad-spectrum activity with selectivity

• Practical development issues:

  • Optimization of pharmacokinetic properties

  • Achieving sufficient tissue penetration at infection sites

  • Balancing potency, specificity, and drug-like properties

• Resistance considerations:

  • While resistance potential is theoretically low due to Obg's essential nature

  • Potential for compensatory mutations or expression changes

  • Need for combination therapy approaches to minimize resistance development

Addressing these challenges requires multidisciplinary approaches combining structural biology, medicinal chemistry, and molecular microbiology.

What types of chemical scaffolds show promise as Obg inhibitors?

Several chemical scaffolds have shown preliminary activity against Obg GTPases:

• Identified chemical classes with activity against Obg GC:

  • Nitrophenyl compounds: 2-chloro-4-nitro-6-{[(E)-2-nitroethenyl]amino}phenol

  • Disulfanyl-tetraazatricyclo compounds: 9-(4-nitrophenyl)-5,13-disulfanyl-2-oxa-4,6,12,14-tetraazatricyclo[8.4.0.0³,⁸]tetradeca-1(10),3,5,7,11,13-hexaene-7,11-diol

  • Natural product derivatives: Garcinol (an EngA inhibitor) has been evaluated against Obg

• Structure-activity relationship considerations:

  • GTP-competitive inhibitors must compete with high intracellular GTP concentrations

  • Allosteric inhibitors targeting regions outside the nucleotide-binding pocket may overcome this challenge

  • Compounds disrupting protein-protein interactions could offer higher selectivity

• Broad-spectrum potential assessment:

  • Active compounds should be evaluated against Obg proteins from multiple pathogens

  • Testing against Klebsiella pneumoniae (Obg KP) and methicillin-resistant Staphylococcus aureus (Obg MRSA) provides important validation

  • Colorimetric and fluorescence-based activity assays can assess cross-species activity

• Optimization strategies:

  • Structure-based design using available structural information

  • Fragment-based approaches to identify novel binding motifs

  • Consideration of physicochemical properties to optimize membrane penetration

Further structure-activity relationship studies and medicinal chemistry optimization efforts are needed to develop these initial scaffolds into clinically relevant compounds.

How can knowledge of Obg structure inform inhibitor design strategies?

Structure-based approaches provide powerful strategies for designing selective Obg inhibitors:

• Key structural features for targeting:

  • The GTP-binding pocket contains the conserved G1-G5 motifs

  • Switch regions undergo conformational changes upon nucleotide binding

  • Potential allosteric sites at domain interfaces

  • RNA-binding surfaces that may be critical for function

• Rational design approaches:

  • GTP-competitive inhibitors targeting the nucleotide-binding pocket

  • Transition state analogs mimicking the GTP hydrolysis state

  • Allosteric inhibitors stabilizing inactive conformations

  • Compounds disrupting critical protein-protein or protein-RNA interactions

• Structure-guided optimization:

  • Molecular docking to predict binding modes

  • Structure-activity relationship analysis to guide chemical modifications

  • Fragment-based approaches to identify novel binding motifs

  • Molecular dynamics simulations to account for protein flexibility

• Targeting Mycoplasma pneumoniae-specific features:

  • Identifying unique structural elements in M. pneumoniae Obg

  • Exploiting differences in surface charge or loop regions

  • Designing compounds that leverage species-specific binding pockets

• Multi-targeting strategies:

  • Designing inhibitors that simultaneously target multiple essential GTPases

  • Dual-action compounds affecting both GTPase activity and ribosome assembly

  • Combination approaches targeting complementary pathways

These structure-based approaches can accelerate the development of potent and selective Obg inhibitors for antimicrobial applications.

What are the future research directions for Mycoplasma pneumoniae Obg?

Several promising research directions will advance our understanding of M. pneumoniae Obg and its potential as a therapeutic target:

• Structural biology:

  • Determination of high-resolution structures of M. pneumoniae Obg in different nucleotide-bound states

  • Cryo-EM studies of Obg-ribosome complexes to understand assembly mechanisms

  • Comparative structural analysis with Obg proteins from other pathogens

• Systems biology approaches:

  • Comprehensive mapping of Obg interaction networks in M. pneumoniae

  • Transcriptomic and proteomic analysis of Obg depletion effects

  • Integration with other -omics data to understand Obg's role in global cellular regulation

• Genome engineering applications:

  • Utilizing RAGE technology to create conditional Obg mutants

  • Development of reporter systems to monitor Obg activity in vivo

  • Engineering M. pneumoniae strains with modified Obg for functional studies

• Therapeutic development:

  • High-throughput screening campaigns to identify novel inhibitor scaffolds

  • Structure-based optimization of lead compounds

  • Development of combination strategies targeting Obg and complementary pathways

• Diagnostic applications:

  • Exploration of Obg as a target for improved molecular diagnostics

  • Development of isothermal amplification methods targeting conserved Obg sequences

  • Point-of-care testing approaches based on Obg detection

These multidisciplinary approaches will deepen our understanding of this essential bacterial protein while advancing its potential as a therapeutic target.

How does Obg research contribute to our broader understanding of bacterial physiology?

Research on Obg GTPases provides insights into fundamental aspects of bacterial physiology:

• Ribosome assembly mechanisms:

  • Obg research has revealed sophisticated quality control mechanisms in ribosome biogenesis

  • Understanding of checkpoint systems ensuring only mature ribosomes participate in translation

  • Insights into the coupling between ribosome assembly and cellular energy status

• Stress response integration:

  • Elucidation of how bacteria coordinate translation with environmental conditions

  • Understanding of bacterial adaptation mechanisms during infection

  • Insights into persistence strategies under adverse conditions

• Evolutionary perspectives:

  • Ribosome assembly GTPases are envisioned to have evolved from the ancestral GTPase along with the translation machinery

  • Comparative studies across species illuminate evolutionary conservation of essential cellular processes

  • Understanding of minimal gene sets required for cellular life

• Therapeutic implications:

  • Identification of vulnerabilities in essential bacterial processes

  • Development of novel antimicrobial strategies targeting conserved GTPases

  • Approaches to combat antimicrobial resistance through new target classes

Obg research thus connects molecular mechanisms to cellular physiology and evolutionary biology, while providing practical applications in infectious disease treatment.

What methodological innovations might advance Obg research in the coming years?

Several emerging technologies and methodological innovations show promise for advancing Obg research:

• Advanced microscopy techniques:

  • Super-resolution microscopy to visualize Obg localization in bacterial cells

  • Single-molecule tracking to monitor Obg dynamics in living bacteria

  • Correlative light and electron microscopy to link function with ultrastructure

• Genomic engineering advances:

  • CRISPR-Cas systems adapted for minimal genome bacteria

  • Base editing approaches for precise manipulation of Obg sequence

  • Inducible degradation systems for temporal control of Obg levels

• Computational approaches:

  • Machine learning algorithms for inhibitor prediction

  • Molecular dynamics simulations at extended timescales

  • Systems biology models integrating multiple cellular processes

• High-throughput functional assays:

  • Microfluidic systems for single-cell analysis of Obg function

  • Droplet-based screening platforms for inhibitor discovery

  • Parallelized biochemical assays for structure-function studies

• Synthetic biology applications:

  • Engineered M. pneumoniae with modified Obg variants for therapeutic applications

  • Development of bacterial chassis strains for lung disease treatments

  • Introduction of synthetic pathways to deliver therapeutic compounds directly to lungs

These methodological innovations will enable deeper mechanistic understanding of Obg function while accelerating therapeutic applications targeting this essential bacterial GTPase.