NOVEL, SPECIFIC O-GLYCOSYLATION OF SECRETED FLAVOBACTERIUM-MENINGOSEPTICUM PROTEINS - ASP-SER-ASTERISK AND ASP-THR-ASTERISK-THR CONSENSUS SITES

A new type of O-linked oligosaccharide has been discovered on several proteins secreted by the Gram-negative bacterium Flavobacterium mening osepticum, including Endo F-2 (three sites), Endo F-3 (one site), and a P40 protease (one site). The oligosaccharide moiety is covalently at tached via a mannose residue to a serine or threonine at consensus sit es corresponding to Asp-Ser or Asp-Thr*-Thr. Preliminary characteriza tion by mass spectroscopy revealed an oligosaccharide of 1244 Da at ea ch of the proposed glycosylation sites. Collision-associated dissociat ion analysis showed a characteristic daughter ion series of m/z 218, 3 94, and 556, indicative of a common Flavobacterium oligosaccharide. Co mpositional analysis demonstrated an unusual profile of monosaccharide s, including hexoses, methylated hexoses, and uronic acid derivatives.