Wzy is a membrane-bound polymerase of 12 TMs, found in Gram-positive bacteria such as Streptococcus pnuemoniae. It forms part of the EPS or exopolysaccharide system. This family is the 6xTMs at the C-terminal end of the molecule. Wzy functions in polymerizing the oligosaccharide repeat subunits to form high-molecular-weight capsular polysaccharides. A contiguous emebrane-bound flippase, Wzx, pfam01943, transports the repeat units to the external surface of the membrane. These polysaccharides form the capsule and their differing compositions contribute to the multidudinous pneumococcal capsular serotypes, all being structurally and antigenically different.