STRUCTURE AND FUNCTION OF THE BACILLUS SPOIIE PROTEIN AND ITS LOCALIZATION TO SITES OF SPORULATION SEPTUM ASSEMBLY

Functioning of the spollE locus of Bacillus subtilis is required for f ormation of a normal polar septum during sporulation and for activatio n of the transcription factor of, which directs early forespore-specif ic gene expression, We have determined the DNA sequence of the wild ty pe and several mutant alleles of the spollE gene of B. subtilis and se quenced a substantial portion of its presumptive homologue in Bacillus megaterium, We show that the spollE locus encodes a single large prot ein with a predicted molecular mass of 92 kDa. Each of five point-muta tion alleles, which have traditionally defined the locus, and two tran sposon-generated mutations were shown to fall within the coding sequen ce for the 92 kDa gene product or within sequences expected to be requ ired for its expression, The aminoterminal portion of the predicted Sp ollE gene product, comprising approximately 40% of the protein, is ext remely hydrophobic and is expected to contain up to 12 membrane-spanni ng segments, The remainder of the protein contains no hydrophobic segm ents long enough to span a lipid bilayer and is therefore presumed to comprise one or more globular, aqueous-phase exposed domains, An in-fr ame fusion joining the 3' end of the B. megaterium spollE coding seque nce to the 5' end of gfp, a gene encoding the green fluorescent protei n (GFP) of Aquorea victoria, resulted in a strong, sporulation-specifi c fluorescent signal localized to the sites of sporulation septum asse mbly, We speculate that SpollE plays a role in assembling the sporulat ion septum, perhaps determining the special properties of the structur e that permit intercompartment signalling during development.