These proteins are found in the endospore-forming bacteria which include Bacillus species. In Bacillus subtilis, ypjB was found to be part of the sigma-E regulon. Sigma-E is a sporulation sigma factor that regulates expression in the mother cell compartment. Null mutants of ypjB show a sporulation defect, but this gene is not, however, a part of the endospore formation minimal gene set.