MOLECULAR ANALYSIS OF THE CAPSULE GENE REGION OF GROUP-A STREPTOCOCCUS - THE HASAB GENES ARE SUFFICIENT FOR CAPSULE EXPRESSION

Enzymes directing the biosynthesis of the group A streptococcal hyalur onic acid capsule are encoded in the hasABC gene cluster. Inactivation of hasC, encoding UDP-glucose pyrophosphorylase in the heavily encaps ulated group A streptococcal strain 87-282, had no effect on capsule p roduction, indicating that hasC is not required for hyaluronic acid sy nthesis and that an alternative source of UDP-glucose is available for capsule production. Nucleotide sequence and deletion mutation analysi s of the 5.5 kh of DNA upstream of hasA revealed that this region is n ot required for capsule expression. Many (10 of 23) group A streptococ cal strains were found to contain insertion element IS1239' approximat ely 50 nucleotides upstream of the -35 site of the hasA promoter. The presence of IS1239' upstream of hasA did not prevent capsule expressio n. These results elucidate the molecular architecture of the group A s treptococcal chromosomal region upstream of the has operon, indicate t hat hasABC are the sole components of the capsule gene cluster, and de monstrate that hasAB are sufficient to direct capsule synthesis in gro up A streptococci.