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  • Title: Structure of a novel glycopeptidolipid antigen containing a O-methylated serine isolated from Mycobacterium xenopi. Complete 1H-NMR and 13C-NMR assignment.
    Author: Rivière M, Augé S, Vercauteren J, Wisingerovà E, Puzo G.
    Journal: Eur J Biochem; 1993 Jun 01; 214(2):395-403. PubMed ID: 8513789.
    Abstract:
    GPL X-1, a novel glycopeptidolipid (GPL) isolated from Mycobacterium xenopi (CIPT 140 35004), has recently been found to typify a new class of mycobacterial glycopeptidolipids devoid of C-mycoside core structure, the so-called serine-containing glycopeptidolipid [Rivière, M. & Puzo, G. (1991) J. Biol. Chem. 266, 9057-9063]. Here we report the purification and characterization of a novel serine-containing GPL termed GPL X-IIb, isolated from the M. xenopi strain NCTC 10042. On thin-layer chromatography, this GPL was found to be present in some other M. xenopi strains isolated from patients with pulmonary infections. The sugar and amino-acid compositions of this GPL were elucidated from the native form using a combination of two-dimensional homonuclear and heteronuclear scalar coupling NMR. The peptide and sugar sequences, as well as the methoxyl group locations on the C-3 of the 6-deoxy-alpha-L-talopyranoside (6dTalp) and on a Ser, were unambiguously determined by heteronuclear multiple-bond correlation experiments. GPL X-IIb was found to be composed of a lipotetrapeptide of the following structure C12-Ser-OMe-Ser-Phe-aThr-OMe (aThr = allothreonine). The sugar part is made up of 3OMe-alpha-L-6dTalp and the following disaccharide: alpha-L-Rhap-(1-->3)-2-O-Lau-alpha-L-Rhap (Rhap = rhanmopyranose). Unlike GPL X-I, the sugar attachment sites on the tetrapeptide were successfully determined from heteronuclear three-bond coupling correlation observed in the heteronuclear multiple bond correlation spectrum between the anomeric carbon resonances and the beta protons of aThr-OMe and Ser. It was established that the 3OMe-6dTalp glycosylates the Ser while the disaccharide is linked to the aThr-OMe. Thus both GPL X-I and GPL X-IIb share a common lipotetrapeptide core [with the exception of Ser(OMe)] but drastically differ in their oligosaccharide appendage. Thus, by analogy with the M. avium complex, the present report suggests that M. xenopi species can be divided in various serovars characterized by the unique structure of their C-mycoside GPL oligosaccharide appendage, enhancing the interest for this new type of serine-containing glycopeptidolipid.
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