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The wprA gene of Bacillus subtilis 168, expressed during exponential growth, encodes a cell-wall-associated protease
1Institut de génétique et de biologie microbiennes, Lausanne, Switzerland.
Abstract:
The nucleotide sequence of wprA, a protease-encoding gene of Bacillus subtilis 168, is reported. The gene, expressed during the exponential growth phase, belongs to a monocistronic operon. WprA is a 96 kDa polypeptide endowed with a signal peptide, as well as a propeptide. Upon processing and export, it gives rise to two previously identified cell-wall-bound proteins, CWBP23 and 52. Processing of WprA exhibits a novel feature of protein export, whereby removal of the middle part of the molecule accompanies the targeting to the cell wall of its N- and C-terminal parts, which correspond to CWBP23 and 52, respectively. Sequence analyses and enzymic assays reveal that CWBP52 is a serine protease. Growth rate, cell morphology, sporulation and motility of wprA mutants apparently do not differ from those of the parent strain.
Insights
The Bacillus subtilis wprA gene encodes a serine protease, CWBP52, with a unique export mechanism. Its processing and cell wall targeting do not affect bacterial growth or sporulation.
Area of Science:
- Microbiology
- Molecular Biology
- Protein Biochemistry
Background:
- Bacillus subtilis is a model organism for studying bacterial genetics and physiology.
- Cell wall-bound proteins play crucial roles in bacterial structure and function.
- The wprA gene product's function and processing were previously uncharacterized.
Purpose of the Study:
- To elucidate the nucleotide sequence and function of the wprA gene in Bacillus subtilis.
- To characterize the protein export and processing mechanism of the WprA polypeptide.
- To determine the enzymatic activity of the processed WprA fragments.
Main Methods:
- Nucleotide sequencing of the wprA gene.
- Analysis of gene expression during bacterial growth phases.
- Protein purification and characterization of WprA and its processed forms.
- Enzymatic assays to determine protease activity.
- Construction and analysis of wprA mutants.
Main Results:
- The nucleotide sequence of wprA was determined, revealing a monocistronic operon structure.
- WprA is synthesized as a 96 kDa precursor with signal and propeptides.
- Processing involves removal of a central part, targeting N-terminal CWBP23 and C-terminal CWBP52 to the cell wall.
- CWBP52 was identified as a serine protease.
- wprA mutants showed no significant differences in growth rate, morphology, sporulation, or motility.
Conclusions:
- WprA is a precursor to cell wall-bound proteins CWBP23 and CWBP52.
- The processing and export of WprA represent a novel mechanism for protein targeting to the bacterial cell wall.
- CWBP52 functions as a serine protease, though its specific role in non-mutant strains remains to be fully elucidated.
- The absence of phenotypic changes in wprA mutants suggests potential functional redundancy or a role in specific environmental conditions not tested.