Interactions of Mycobacterial Glycopeptidolipids with Membranes: Influence of Carbohydrate on Induced Alterations

• Published in: Biochemistry (Easton) Vol. 33; no. 23; pp. 7056 - 7061
• Main Authors: Lopez-Marin, Luz Maria, Quesada, Dolores, Lakhdar-Ghazal, Faouzi, Tocanne, Jean-Francois, Laneelle, Gilbert
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 01.06.1994
• Subjects: Animals; Carbohydrate Metabolism; Carbohydrate Sequence; Cell Membrane - metabolism; Cell Membrane - physiology; Cell Membrane Permeability; Glycopeptides - metabolism; Membrane Lipids - metabolism; Membrane Potentials; Molecular Sequence Data; Mycobacterium; Mycobacterium - metabolism; Oxidative Phosphorylation; Rats
• ISSN: 0006-2960; 1520-4995
• DOI: 10.1021/bi00189a006

Glycopeptidolipids (GPLs) are specific constituents of mycobacteria known as opportunistic pathogens. The influence of the carbohydrate moiety on GPL-induced membrane alterations was examined with GPLs bearing 1-5 sugar residues (GPL-1 to GPL-5) and a sulfated GPL (S-GPL-2). GPLs decreased the ADP/O ratio and increased controlled respiration of isolated mitochondria. The more polar GPLs were the less active, with the following order of efficiency: GPL-1 > GPL-2 > S-GPL-2 = GPL-3 = GPL-5. GPL-1 and GPL-2 increased passive permeability of liposomes to carboxyfluorescein (GPL-1 > GPL-2), while GPL-3 and GPL-5 were inactive. GPL-2 and GPL-3 decreased the transmembrane electrical potential (delta psi) in isolated mitochondria (GPL-2 > GPL-3). These results suggest that GPLs uncouple oxidative phosphorylation by increasing the passive permeability of the mitochondrial membrane to protons. Compression isotherms of GPL-2 monolayers showed that, at low surface pressure, the area per GPL-2 molecule was about 5 times that of an acyl chain: it is likely that the peptide moiety was at the air/water interface. With an increase in the surface pressure, its area decreased, down to that of a tightly packed acyl chain. It is postulated that the glycopeptidic moiety can be either at in the interface or dipping into the water.