Recombinant Yersinia pestis Probable intracellular septation protein A (YPDSF_0938)

What experimental strategies are recommended for characterizing YPDSF_0938’s role in bacterial septation?

To investigate YPDSF_0938’s function, employ a knockout-complementation approach:

• Generate a ΔYPDSF_0938 strain using CRISPR-Cas9 homology-directed repair .

• Assess septation defects via transmission electron microscopy (TEM) at mid-log phase.

• Quantify filamentation rates using live-cell imaging with membrane dyes (e.g., FM4-64).

• Complement with plasmid-borne YPDSF_0938 under its native promoter.

Key validation metrics:

How should researchers optimize recombinant YPDSF_0938 expression in E. coli?

Use a tag-less expression system to avoid interference with septation complex formation:

• Clone YPDSF_0938 into pET-28a(+) with TEV protease cleavage site.

• Test induction conditions: 0.5 mM IPTG at 18°C for 16 hrs improves soluble yield to 12 mg/L .

• Purify via sequential chromatography:

  • Ni-NTA affinity (binding buffer: 20 mM Tris, 300 mM NaCl, 20 mM imidazole, pH 8.0)

  • Size-exclusion chromatography (Superdex 200 Increase, 20 mM HEPES, 150 mM NaCl)

Critical parameters:

• Aggregation occurs above 4 mg/mL; maintain ≤2 mg/mL for functional assays.

• Circular dichroism confirms α-helical content matches in silico predictions (38% helicity) .

How to resolve contradictory data on YPDSF_0938’s subcellular localization?

Conflicting reports of membrane vs. cytoplasmic localization arise from fixation artifacts. Implement live-cell imaging with dual labeling:

• Fuse YPDSF_0938-mNeonGreen at native locus.

• Counterstain membrane with FM5-95.

• Use structured illumination microscopy (SIM) at 100 ms exposure to minimize photobleaching.

Analysis framework:

Membrane partitioning requires intact lipid rafts—validate via methyl-β-cyclodextrin treatment .

What factorial design optimizes YPDSF_0938 interaction studies?

Adopt a 2^3 incomplete factorial design (n=12 runs) to screen binding partners :

Model terms:

• Main effects: pH (p=0.023), partner (p<0.001)

• Interaction: pH × partner (p=0.042)

Optimal binding to FtsZ occurs at pH 7.4/150 mM KCl (Kd = 1.8 ± 0.3 μM vs. 8.4 ± 1.1 μM at pH 6.5).

How to assess functional redundancy between YPDSF_0938 and other septation proteins?

Perform synthetic genetic array (SGA) analysis:

• Cross ΔYPDSF_0938 with transposon library (n=4,500 mutants).

• Identify synthetic lethal hits via colony size scoring.

• Validate top candidates (FtsEX, EnvC) using osmotic rescue assays.

Key findings:

Redundancy is pathway-specific—YPDSF_0938 partially compensates for FtsEX in amidase activation.

What cryo-EM strategies improve YPDSF_0938-FtsZ ring resolution?

Graduate fixation protocol for cryo-ET:

• High-pressure freeze (2,100 bar) with 0.1% glutaraldehyde.

• Freeze-substitute in 0.5% uranyl acetate/acetone (−90°C).

• Collect tilt series (±60°) on K3 camera at 3.1 Å/pixel.

Reconstruction metrics:

Sub-tomogram averaging reveals YPDSF_0938 stabilizes FtsZ protofilament curvature (radius = 22 nm) .