Molecular cloning, identification, and sequence of the hyaluronan synthase gene from group A Streptococcus pyogenes

The hyaluronan (HA) synthase of Group A Streptococci has been identified by transposon mutagenesis and deletion analysis. The genes for the HA synthase and a recently identified UDP-Glc dehydrogenase (Dougherty, B. A., and van de Rijn, I. (1993) J. Biol. Chem. 268, 7118-7124) reside on a contiguous stretch of 3.2-kilobase pair DNA that can direct HA biosynthesis in Enterococcus faecalis and Escherichia coli as well as mutant Streptococcus (DeAngelis, P. L., Papaconstantinou, J., and Weigel, P. H. (1993) J. Biol. Chem. 268, 14568-14571). The synthase contains 395 residues (calculated M_r = 45,063) and migrates on SDS-PAGE with a molecular mass of 42 kDa. E. coli K5, which synthesizes UDP-glucuronic acid for production of its endogenous capsular polysaccharide, can make HA if it contains a plasmid encoding the intact 42-kDa protein. E. coli SURE or _χ1448 cells containing the same construct, however, cannot produce HA since these strains cannot make both required sugar nucleotide precursors. The HA synthase is predicted to be an integral membrane protein with four membrane-associated helices, which is consistent with the location of the enzyme activity in Streptococci. There is significant homology between the HA synthase and the Rhizobium nodC gene product, an enzyme that synthesizes chitin-like oligomers. This is the first description at the molecular level of an enzyme shown to synthesize a glycosaminoglycan.