STRUCTURE AND SPECIFIC ACTIVITY OF MACROPHAGE-STIMULATING LIPOPEPTIDES FROM MYCOPLASMA-HYORHINIS

Mycoplasmas are potent macrophage stimulators. We describe the isolati on of macrophage-stimulatory lipopeptides S-[2,3-bisacyl(C-16:0/C-18:0 )oxypropyl] cysteinyl-GQTDNNSSQSQQPGSGTTNT and S-[2,3-bisacyl (C-16:0/ C-18:0)oxypropyl] cysteinyl-GQTN derived from the Mycoplasma hyorhinis variable lipoproteins VlpA and VlpC, respectively. These lipopeptides were characterized by amino acid sequence and composition analysis an d by mass spectrometry, The lipopeptides S- [2,3-bis(palmitoyloxy) pro pyl] cysteinyl-GQTNT and S-[2,3-bis(palmitoyloxy)propyl] cysteinyl-SKK KK and the N-palmitoylated derivative of the latter were synthesized, and their macrophage-stimulatory activities were compared in a nitric oxide release assay with peritoneal macrophages from C3H/HeJ mice. The lipopeptides with the free amino terminus showed half-maximal activit y at 3 pM regardless of their amino acid sequence; i.e., they were as active as the previously isolated hi. fermentans-derived lipopeptide M ALP-2. The macrophage-stimulators activity of the additionally N-palmi toylated lipopeptide or of the murein lipoprotein from Escherichia col i, however, was lower by orders of magnitude. It is concluded that the lack of N-acyl groups in mycoplasmal lipoproteins explains their exce ptionally high in vitro macrophage-stimulatory capacity. Certain featu res that lipopolysaccharide endotoxin and mycoplasmal lipopeptides hav e in common are discussed. Lipoproteins and lipopeptides are likely to be the main causative agents of inflammatory reactions to mycoplasmas . This may be relevant in the contest of mycoplasmas as arthritogenic pathogens and their association with AIDS.