FIG 3.

Structural and genetic comparative analysis identifies putative determinants of 36A versus 36B capsule types. (A) Graphical representation of structurally resolved pneumococcal capsule polysaccharide (PS) repeat units that contain features putatively mediated by 36A/36B capsule biosynthetic (cps) locus gene homologs. For clarity, capsule PS O-acetylation is not depicted, and capsule types with identical de-O-acetylated capsule PS structures (e.g., 9V and 9A, etc.) are listed together. Structural features shared by different capsule types are highlighted by alike colored boxes. Glycosidic bonds predicted to be catalyzed by each cps-encoded glycosyltransferase (GT) (see the text) are labeled in red. Features dictated by initial GTs (blue) and polymerases (green) are also labeled. Dotted boxes in the 36A and 9N repeat units denote the predicted factor 9e antigenic determinant (“9e”). (B) Alignment of amino acid sequences encoded by wcjA alleles from cps loci representing listed serotypes and from Streptococcus mitis (S. mitis). For clarity, only portions containing residues associated with factor 9e (highlighted in gray) are shown. The grid on the right shows pairwise percent amino acid identity between the complete wcjA-encoded GTs.