Functional identification of the product of the Bacillus subtilis yvaL gene as a SecG homologue

Protein export in Escherichia coli is mediated by translocase, a multisubun it membrane protein complex with SecA as the peripheral subunit and the Sec Y, SecE, and SecG proteins as the integral membrane domain. In the gram-pos itive bacterium Bacillus subtilis, SecA, SecY, and SecE have been identifie d through genetic analysis. Sequence comparison of the Bacillus chromosome identified a potential homologue of SecG, termed YvaL. A chromosomal disrup tion of the yvaL gene results in mild cold sensitivity and causes a beta-la ctamase secretion defect. The cold sensitivity is exacerbated by overexpres sion of the secretory protein alpha-amylase, whereas growth and beta-lactam ase secretion are restored by coexpression of yvaL or the E. coli secG gene . These results indicate that the yvaL gene codes for a protein that is fun ctionally homologous to SecG.