A new glycosylated lipopeptide incorporated into the cell wall of a smooth variant of Gordona hydrophobica

Abstract

A cell wall component of a smooth variant of Gordona hydrophobica 1775/15 was isolated and purified, and its structure was determined by various chemical methods, including chemical synthesis of part structures, Edman degradation, gas chromatography/mass spectrometry analysis, matrix- assisted laser desorption ionization, post-source decay (MALDI-PSD) tandem mass spectrometry, and 1H and 13C NMR using one- and two-dimensional, homo- and heteronuclear correlated spectroscopy. The cell wall component was found to be a (mono-) glycosylated peptidolipid (GPL) consisting of a tridecapeptide interlinked by a β-hydroxylated fatty acid (3- hydroxyeicosanoic acid, 20:0 (3-OH)) to form a cyclic lactone ring structure. The main fraction of GPL, for which we propose the name gordonin, was identified as 3-hydroxyeicosanoyl-L-seryl-L-phenylalanyl-L-seryl-L-seryl-D- alanyl-L-(O-β-D-glucopyranosyl)-threonyl-glycyl-D-leucyl-L-valyl-L-seryl-L- phenylalanyl-glycyl-L-valyl lactone. The other GPLs constitute structural variations within the nature of the β-hydroxylated fatty acid (20: 0(3-OH) versus 22:1(3-OH)) in a ratio of about 1:0.9 as well as within one amine acid (D-Leu versus L-Phe) in about 30%. Sequence information was obtained in part by Edman degradation as well as gas chromatography/mass spectrometry analysis of di- and tripeptide fragments. However, the complete amine acid sequence could only be established by MALDI-PSD from the linear molecule, i.e. after ring opening of the lactone. In contrast, rough variants of G. hydrophobica 1775/15 lack these peptidolipids or synthesize them to a much lesser extent indicating that gordonin contributes significantly to the physicochemical character of the cell surface.