This is the structural middle domain of Stage IV sporulation protein A (SpoIVA) which follows the ATPase domain and the predicted secondary structure suggests that it is composed of two symmetrical units containing alpha-helices and beta-strands [1]. SpoIVA acts in the mother cell compartment and plays a role in spore coat morphogenesis. A comparative genome analysis of all sequenced genomes of Firmicutes shows that the proteins are strictly conserved among the sub-set of endospore-forming species [1,2].

1: ATP hydrolysis by a domain related to translation factor GTPases drives polymerization of a static bacterial morphogenetic protein. Castaing JP, Nagy A, Anantharaman V, Aravind L, Ramamurthi KS; Proc Natl Acad Sci U S A. 2013;110:E151-E160. PMID:23267091

2: A four-dimensional view of assembly of a morphogenetic protein during sporulation in Bacillus subtilis. Price KD, Losick R; J Bacteriol. 1999;181:781-790. PMID:9922240