Interactions of mycobacterial glycopeptidolipids with membranes: influence of carbohydrate on induced alterations.
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.(ABSTRACT TRUNCATED AT 250 WORDS)
Lopez-Marin
L M
LM
Laboratoire de Pharmacologie et Toxicologie Fondamentales du CNRS, Toulouse, France.
Quesada
D
D
Lakhdar-Ghazal
F
F
Tocanne
J F
JF
Lanéelle
G
G
D000818:Animals; D050260:Carbohydrate Metabolism; D002240:Carbohydrate Sequence; D002462:Cell Membrane / Q000378:metabolism / Q000502:physiology; D002463:Cell Membrane Permeability; D006020:Glycopeptides / Q000378:metabolism*; D008563:Membrane Lipids / Q000378:metabolism*; D008564:Membrane Potentials; D008969:Molecular Sequence Data; D009161:Mycobacterium / Q000378:metabolism*; D010085:Oxidative Phosphorylation; D051381:Rats
D006020:Glycopeptides; D008563:Membrane Lipids