Molecular characterization of hasA from an operon required for hyaluronic acid synthesis in group A streptococci.
The mechanism by which group A streptococci produce the antiphagocytic hyaluronate (hyaluronic acid) capsule is incompletely understood. Enzymes known to be essential for synthesis of this polysaccharide include the membrane-associated hyaluronate synthase as well as those required for production of the substrate sugars UDP-N-acetylglucosamine and UDP-glucuronic acid. In this study, a Tn916 insertion that inactivates hyaluronate synthetic activity was localized to a gene designated hasA in the hyaluronic acid synthesis operon. This gene has recently been preliminarily identified as the group A streptococcal hyaluronate synthase. The DNA sequence and transcription start site of hasA were determined, and the predicted HasA protein was shown to have characteristics of a membrane protein. Amino acid sequence homology suggests that HasA is related to a family of proteins involved in polysaccharide production and cell differentiation. Finally, in addition to the loss of hyaluronate synthase activity, the hasA::Tn916 insertion was demonstrated to correlate with a loss of UDP-glucuronic acid dehydrogenase activity. These results suggest that the genes required for hyaluronate synthase activity and production of the UDP-glucuronic acid substrate are transcribed as a unit in group A streptococci.
Dougherty
B A
BA
Wake Forest University Medical Center, Winston-Salem, North Carolina 27157.
van de Rijn
I
I
D000595:Amino Acid Sequence; D001483:Base Sequence; D004251:DNA Transposable Elements; D004269:DNA, Bacterial; D014453:Glucuronosyltransferase / Q000235:genetics* / Q000378:metabolism; D016695:Glycosyltransferases; D000076002:Hyaluronan Synthases; D006820:Hyaluronic Acid / Q000096:biosynthesis* / Q000235:genetics*; D008565:Membrane Proteins; D008969:Molecular Sequence Data; D009876:Operon; D011401:Promoter Regions, Genetic; D017386:Sequence Homology, Amino Acid; D013297:Streptococcus pyogenes / Q000378:metabolism*; D014158:Transcription, Genetic; D014166:Transferases; D029867:Xenopus Proteins
D004251:DNA Transposable Elements; D004269:DNA, Bacterial; D008565:Membrane Proteins; D029867:Xenopus Proteins; D006820:Hyaluronic Acid; D014166:Transferases; D016695:Glycosyltransferases; D014453:Glucuronosyltransferase; C056944:HAS1 protein, Xenopus; D000076002:Hyaluronan Synthases