Structure of the Escherichia coli K2 capsular antigen, a teichoic acid-like polymer.

The primary structure of the K2 antigen of Escherichia coli was elucidated by composition, alkaline fragmentation, dephosphorylation with hydrofluoric acid, periodate oxidation, and methylation analysis. The polymer contains galactose in the pyranosidic and furanosidic ring form. It consists of phosphogaolactopyranosyl glycerol and phosphagalactofuranosyl glycerol units in a molar ratio of 2:1. The sequence of these units is not known. The structure of the K2 antigen is reminiscent of that of certain teichoic acids of gram-positive bacteria. Using microprecipitation, it was shown that in the polymer galactoside is immunodominant.