This is the N-terminal region of YpeB, a protein restricted to endospore-forming species in the Firmicutes lineage of bacteria, that have been found in all such species to date except Clostridium perfringens. YpeB and the spore-cortex-lytic enzyme SleB are required for normal germination [1]. This protein is essential in stabilising SleB enzyme in Bacillus spores, and may regulate its activity during germination [1].

1: Crystal structure of the PepSY-containing domain of the YpeB protein involved in germination of bacillus spores. Ustok F, Chirgadze D, Christie G. Proteins. 2015;83(10):1914-21 PMID:26219275