Recombinant Leptotrichia buccalis ATP-dependent zinc metalloprotease FtsH (ftsH)

What are the structural characteristics of Leptotrichia buccalis ATP-dependent zinc metalloprotease FtsH?

Leptotrichia buccalis ATP-dependent zinc metalloprotease FtsH is a full-length protein consisting of 768 amino acids (1-768aa). The complete amino acid sequence is: MADRDKNDIRKRLEELRKDNNRRNNRQDNGNRSPFSGFLFFIFVILLFTFTLLFHRDIQTYFQEKREISYTEFVSKTQKGDFSEINEKDDKLISQVKENGKDVLYYTKKITDRVGDEPNIISAIGQKKVKLNSLQPSGGGFFLLLLGQFLPMIIMIGLMVYLAKKMVGGSQGGGPGNIFGFGKSRVNKIDKKPDVKFDDVAGVDGAKEELREVVDFLKNPEKYTKAGARVPKGVLLLGRPGTGKTLLAKAVAGESGASFFSISGSEFVEMFVGVGASRVRDLFEKAKESSPSIIFIDEIDAIGRRRSVGKNSGSNDEREQTLNQLLVEMDGFETDTKVIVLAATNREDVLDPALLRAGRFDRRVTVDAPDLQGRIAILKVHSRNKKLARDVKLEDIAKITPGFVGADLANLLNEAAILAAARRASDTIKMADLDEAVDKIGMGLGQKGKIIKPEEKKLLAYHEAGHAIMTELTPGADPVHKVTIIPRGDAGGFMMPLPEEKLVTTSRQMLAEIKVLFGGRAAEEIGLEDVSTGAYSDIKRATKVARAYVESVGMSKKLGPINFENSDDEYSFTPNKSDETVREIDLEIRKILTEEYFNTLNTLQDNWEKLEQVVELLLKKETITGDEVRRIIAGEKAEDILKGTEVKEESIQKGSEGIVQTENSIEESQENKTVEAEVHDSNLKSDTEKLAEAVREITGETGGVLEPTEKNDFDKDSDDNEKNDDDNENSDDSSKNDSDSDDENENSDNKSEKNKKRKSNFKLPSFME . As part of the AAA+ (ATPases Associated with diverse cellular Activities) protein family, FtsH contains an ATPase domain for energy generation and a metalloprotease domain responsible for its proteolytic activity. The protein structure includes transmembrane regions that anchor it to membranes in its native state.

What expression systems are commonly used for producing recombinant Leptotrichia buccalis FtsH?

Recombinant Leptotrichia buccalis FtsH can be produced in multiple expression systems, each offering distinct advantages for different research applications. The most common expression system is Escherichia coli, which provides high yields and relatively straightforward purification protocols . Other available expression systems include Yeast, Baculovirus, and Mammalian cells . When choosing an expression system, researchers should consider the downstream applications of the protein. E. coli-expressed protein is suitable for most structural and functional studies, while mammalian or baculovirus systems may provide more appropriate post-translational modifications for interaction studies or when investigating eukaryotic cellular environments. The expression system choice affects protein folding, solubility, and biological activity, making it a critical decision point in experimental design.

How should recombinant Leptotrichia buccalis FtsH be stored to maintain optimal activity?

For optimal activity maintenance, recombinant Leptotrichia buccalis FtsH should be stored as follows:

• Long-term storage: Store at -20°C/-80°C upon receipt, with aliquoting necessary for multiple use to avoid repeated freeze-thaw cycles.

• Working aliquots: Store at 4°C for up to one week.

• Storage buffer: Tris/PBS-based buffer with 6% Trehalose, pH 8.0.

• Reconstitution: The lyophilized powder should be briefly centrifuged prior to opening to bring contents to the bottom, then reconstituted in deionized sterile water to a concentration of 0.1-1.0 mg/mL.

• For long-term storage of reconstituted protein: Add 5-50% glycerol (final concentration) and aliquot before storing at -20°C/-80°C .

Repeated freeze-thaw cycles significantly reduce enzyme activity and should be strictly avoided. The addition of glycerol serves as a cryoprotectant that helps preserve protein structure during freezing.

What purification methods are most effective for isolating recombinant Leptotrichia buccalis FtsH?

The most effective purification strategy for recombinant Leptotrichia buccalis FtsH employs affinity chromatography based on the attached tag. For His-tagged versions, immobilized metal affinity chromatography (IMAC) using Ni-NTA or Co-NTA resins is the method of choice . The purification protocol typically includes:

• Cell lysis under native or denaturing conditions depending on protein solubility

• Binding to affinity resin in buffer containing low imidazole concentrations (10-20 mM)

• Washing steps with increasing imidazole concentrations to remove weakly bound contaminants

• Elution with high imidazole (250-500 mM)

• Buffer exchange to remove imidazole via dialysis or gel filtration

For higher purity requirements (>90%), additional purification steps such as ion exchange chromatography or size exclusion chromatography are recommended. The purified protein should be analyzed by SDS-PAGE to confirm purity, with expected purity levels of at least 85-90% .

How does the phosphorylation state of FtsH affect its proteolytic activity and what methods can be used to analyze this?

The phosphorylation state of FtsH appears to correlate with its oligomerization degree rather than being dependent on light exposure or major thylakoid protein kinases like STN7 and STN8 . To analyze FtsH phosphorylation status and its effects on proteolytic activity, researchers can employ the following methodologies:

• Phosphorylation state analysis: Phos-tag SDS-PAGE followed by immunoblot analysis effectively separates phosphorylated and non-phosphorylated forms of FtsH . This technique involves incorporating Phos-tag molecules into polyacrylamide gels, which specifically bind phosphorylated proteins and retard their migration.

• Correlation with activity: To assess how phosphorylation affects proteolytic activity, researchers can perform in vitro proteolysis assays using:

  • Purified phosphorylated and non-phosphorylated FtsH fractions

  • Known FtsH substrates labeled with fluorescent tags

  • Quantitative measurement of substrate degradation rates

• Site-directed mutagenesis: Creating phosphomimetic (e.g., Ser/Thr to Asp/Glu) or phospho-null (Ser/Thr to Ala) mutations at predicted phosphorylation sites allows for functional analysis of specific phosphorylation events. Evidence suggests that mutations in predicted phosphorylation sites can affect protein function, as demonstrated in plant systems where such mutations failed to rescue mutant phenotypes .

• Mass spectrometry: LC-MS/MS analysis following enrichment of phosphopeptides can identify specific phosphorylation sites and their stoichiometry, providing insights into regulatory mechanisms.

What is the role of Leptotrichia buccalis FtsH in bacterial physiology and pathogenesis?

Leptotrichia buccalis FtsH plays crucial roles in bacterial physiology and may contribute to pathogenesis through several mechanisms:

• Protein quality control: As an ATP-dependent zinc metalloprotease, FtsH participates in the degradation of misfolded or damaged proteins, maintaining proteostasis within the bacterial cell.

• Regulation of membrane proteins: FtsH typically localizes to membranes and regulates membrane protein composition by selectively degrading certain integral membrane proteins.

• Stress response: FtsH contributes to bacterial adaptation to environmental stresses by removing stress-damaged proteins and regulating stress response pathways.

• Pathogenesis connection: Recent studies have found significant transcript abundance of Leptotrichia buccalis in severe COVID-19 patients, suggesting a potential association with disease severity . This observation indicates that L. buccalis, and potentially its expressed proteins including FtsH, might contribute to inflammatory responses and co-infections that could modulate disease severity.

To investigate these roles experimentally, researchers can:

• Create conditional knockout strains to observe phenotypic changes

• Perform transcriptomic and proteomic analyses under different stress conditions

• Study interaction partners of FtsH using co-immunoprecipitation followed by mass spectrometry

• Analyze the effect of FtsH inhibition on bacterial survival in infection models

How can recombinant Leptotrichia buccalis FtsH be used to study protease-substrate interactions?

Recombinant Leptotrichia buccalis FtsH provides a valuable tool for investigating protease-substrate interactions through several methodological approaches:

• In vitro degradation assays:

  • Purified recombinant FtsH can be incubated with potential substrate proteins

  • Substrate degradation can be monitored by SDS-PAGE, western blotting, or using fluorescently labeled substrates

  • Kinetic parameters (Km, Vmax) can be determined through time-course experiments with varying substrate concentrations

• Substrate specificity analysis:

  • Peptide library screening with recombinant FtsH to identify preferred cleavage motifs

  • Comparing degradation efficiency of wild-type versus mutated substrates to identify recognition elements

  • Competitive degradation assays with multiple substrates to determine preference hierarchy

• Structure-function studies:

  • Site-directed mutagenesis of the catalytic domain to identify residues critical for substrate recognition

  • Creating chimeric proteins with FtsH domains from different species to determine specificity determinants

  • Crystallography or cryo-EM studies of FtsH-substrate complexes using catalytically inactive mutants

• Interaction analysis:

  • Surface plasmon resonance (SPR) to measure binding kinetics between FtsH and substrates

  • Hydrogen-deuterium exchange mass spectrometry to identify interaction interfaces

  • Crosslinking coupled with mass spectrometry to capture transient interactions

When designing these experiments, it's important to consider that the recombinant protein (typically His-tagged) may have different properties than the native enzyme . Control experiments comparing activity of tagged versus untagged versions can help address this concern.

What are the comparative functional differences between FtsH from Leptotrichia buccalis and other bacterial species?

FtsH metalloproteases are highly conserved across bacterial species, but exhibit functional specializations that can be studied using comparative approaches:

• Substrate specificity:

  • L. buccalis FtsH likely has distinct substrate preferences compared to well-studied homologs from E. coli or B. subtilis

  • Comparative degradation assays using recombinant FtsH proteins from different species against a panel of substrates can reveal specificity differences

  • Sequence analysis and structural modeling can identify variations in substrate-binding regions

• Regulatory mechanisms:

  • Phosphorylation appears to be an important regulatory mechanism for FtsH activity, with variations across species

  • The relationship between phosphorylation and oligomerization observed in some systems should be investigated in L. buccalis FtsH

  • Other potential regulatory mechanisms include cofactor requirements, membrane composition effects, and protein-protein interactions

• Physiological roles:

  • While FtsH serves protein quality control functions across species, its importance in specific cellular processes may vary

  • In L. buccalis, FtsH may have specialized roles related to the organism's adaptation to the oral microbiome

  • Transcriptomic data indicates L. buccalis is present in severe COVID-19 patients, suggesting potential roles in host-microbe interactions

• Structural comparisons:

  • The full-length sequence of L. buccalis FtsH (768 amino acids) provides the basis for structural comparison with other FtsH proteins

  • Homology modeling using solved crystal structures from other bacterial FtsH proteins can highlight structural differences

  • Key domains to compare include the ATPase domain, protease domain, and transmembrane regions

To conduct these comparative studies effectively, researchers should express and purify FtsH from multiple bacterial species under identical conditions, ensuring that expression systems and tags are consistent to minimize methodological variables.

How can recombinant Leptotrichia buccalis FtsH be used in drug discovery targeting bacterial proteases?

Recombinant Leptotrichia buccalis FtsH offers several applications in drug discovery targeting bacterial proteases:

• High-throughput inhibitor screening:

  • Development of fluorescence-based assays using recombinant FtsH and fluorogenic peptide substrates

  • Screening of compound libraries to identify molecules that inhibit proteolytic activity

  • Structure-activity relationship studies on promising lead compounds

• Rational drug design:

  • Structural studies (X-ray crystallography, cryo-EM) of recombinant FtsH to identify druggable pockets

  • In silico molecular docking with virtual compound libraries

  • Fragment-based drug design targeting the ATP-binding or catalytic zinc-binding sites

• Differential inhibition profiling:

  • Comparing inhibition profiles against FtsH from multiple bacterial species versus human homologs

  • Identifying compounds with selectivity for bacterial FtsH over human counterparts

  • Testing against FtsH from pathogenic species to establish spectrum of activity

• Validation methodologies:

  • Thermal shift assays to confirm direct binding of compounds to recombinant FtsH

  • Surface plasmon resonance to determine binding kinetics

  • Cellular assays using bacteria expressing fluorescently tagged FtsH substrates to confirm target engagement in vivo

• Application in the context of clinical findings:

  • Given the association of L. buccalis with severe COVID-19 patients , developing inhibitors targeting its proteases could have therapeutic potential

  • Investigating whether FtsH inhibition affects bacterial survival under conditions mimicking the respiratory environment

When designing screening campaigns, researchers should consider both the ATPase and protease activities of FtsH, as either function could be targeted for inhibition. Additionally, the multimeric nature of active FtsH complexes presents opportunities for developing inhibitors that disrupt oligomerization.