Structure of type 3Gn coaggregation receptor polysaccharide from Streptococcus cristatus LS4

The presence of a novel coaggregation receptor polysaccharide (RPS) on the dental plaque isolate Streptococcus cristatus LS4 was suggested by this strain’s antigenic and coaggregation properties. Examination of RPS isolated from strain LS4 by a combination of 2-dimensional and pseudo 3-dimensional single quantum heteronuclear NMR methods that included detection of ¹³C chemical shifts at high resolution revealed the following repeat unit structure:→6)-β-d-Galf-(1→6)-β-d-GalpNAc-(1→3)-α-d-Galp-(1→P→6)-α-d-Galp-(1→3)-β-L-Rhap-(1→4)-β-d-Glcp-(1→.The identification of this polysaccharide as RPS3Gn, a new structural type, was established by the α-d-Galp-containing epitope of RPS serotype 3 and Gn recognition motif (i.e., β-d-GalpNAc (1→3)-α-d-Galp) for coaggregation with other bacteria.