Molecular discrimination between Neisseria meningitidis serogroups W-135 and Y based on the nucleotide recognition domain sequence of the capsule polymerases.

摘要

Pathogenic Neisseria meningitidis isolates in most cases express one of five capsular polysaccharide-defined sero-groups, i.e., A, B, C, W-135, and Y. The capsular polysac-charides of serogroups W-135 and Y are composed of repetitive disaccharide units of sialic acid linked to galactose and glucose, respectively (1). The capsule polymerases and the encoding genes synF and synG (also referred to as si-aD_(W-135) and siaD_Y, respectively) are closely related (5). We recently demonstrated that a single amino acid at position 310 in the N-terminal glycosyltransferase domain of the capsule polymerases is responsible for substrate specificity toward UDP-galactose or UDP-glucose (4). Amino acid 310 is part of the EX_7E motif characteristic for the nucleotide recognition domain within glycosyltransferases (6). 310P determines the serogroup W-135 capsule, and 310G determines the serogroup Y capsule. Others furthermore demonstrated that the capsule polymerase of strains that expressed a mixed galactose/glucose-sialic acid polysaccharide were associated with 310S (11).