The structure of the cyclic enterobacterial common antigen (ECA) from Yersinia pestis.
Two antigenic acidic polysaccharides related to enterobacterial common antigen (ECA) were isolated from a vaccine strain of a pathogenic microorganism Yersinia pestis. The low molecular weight polysaccharide (LMP) is composed of equal amounts of 2-acetamido-2-deoxy-D-mannuronic acid, 4-acetamido-4,6-dideoxy-D-galactose (Fuc4NAc), and 2-amino-2-deoxy-D-glucose which is partially N- and partially 6-O-acetylated. The structure of the trisaccharide repeating unit was established by analyses of LMP and the completely N-acetylated LMP (LMP-NAc) using 1H and 13C NMR spectroscopy, including 2D COSY and 1D NOE spectroscopy. Deamination of LMP with nitrous acid gave a set of oligomers terminated with 2,5-anhydromannose and ranging from tri- to dodeca-saccharides, thus indicating a random distribution of free amino groups. FABMS analyses of LMP and LMP-NAc showed that LMP consists mainly of the cyclic tetramer of the trisaccharide repeating unit together with a small amount of the cyclic trimer and a very small amount of the cyclic pentamer and has, thus, the following structure: [formula: see text] where R is Ac or H (approximately 1:1), R' is Ac or H (approximately 1:4), and n = 4 (major), 3, 5 (minor). Small proportions of the linear trimer and the linear tetramer were also detected in the preparations. The high molecular weight polysaccharide is linear and has the same (or a very similar) repeating unit as LMP.
Institute of Immunology, Ministry of Health, Moscow, Russian Federation.
E V
EV
Vinogradov
Y A
YA
Knirel
J E
JE
Thomas-Oates
A S
AS
Shashkov
V L
VL
L'vov
D000942:Antigens, Bacterial / Q000737:chemistry* / Q000302:isolation & purification; D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D002241:Carbohydrates / Q000032:analysis; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000737:chemistry / Q000302:isolation & purification; D011135:Polysaccharides, Bacterial / Q000737:chemistry* / Q000302:isolation & purification; D016339:Spectrometry, Mass, Fast Atom Bombardment; D014312:Trisaccharides / Q000737:chemistry / Q000302:isolation & purification; D015010:Yersinia pestis / Q000737:chemistry / Q000276:immunology*
D000942:Antigens, Bacterial; D002241:Carbohydrates; D009844:Oligosaccharides; D011135:Polysaccharides, Bacterial; D014312:Trisaccharides; C017286:enterobacterial common antigen