Primary Structure of a New Phosphocholine-containing Glycoglycerolipid of Mycoplasma fermentans

Abstract

The human pathogen Mycoplasma fermentans PG18 was isolated from the urogenital tract several decades ago (1). Because of reports indicating its possible role as a cofactor accelerating the progression of human immunodeficiency virus disease, its significance as a pathogen in other immunocompromised patients (2), and its role in the pathogenesis of rheumatoid arthritis, interest in M. fermentans has recently increased (3). Although little is known of the molecular mechanisms underlying M. fermentans pathogenicity (4), it has been shown that human immunodeficiency virus-associated cytopathic effects could be increased by the presence of M. fermentans (2) and that M. fermentans is capable of fusing with T-cells and peripheral lymphocytes (5).It is reasonable to assume that Mycoplasma membrane components are involved in the attachment and fusion of the microbe with eukaryotic host cells. Salman et al. (6) isolated an unusual phospholipid from the cell membranes of M. fermentans and showed that this material (compound X) was capable of enhancing the fusion of small, unilamellar vesicles with MOLT-3 lymphocytes in a dose-dependent manner.Matsuda et al. (4) isolated two glycoglycerolipids (GGPL-I 1 and GGPL-III) from M. fermentans. GGPL-I structure was shown to be 6Ј-O-phosphocholine-␣-D-glucopyranosyl-1,2-diacyl-sn-glycerol (7) as elucidated by mass and NMR spectroscopy. It was later shown (4) that the structure of a more polar glycolipid (GGPL-III) isolated from the same strain of M. fermentans was very similar to that of GGPL-I. The chemical structure of GGPL-III, however, has so far remained obscure. The only distinguishing structural feature known is that it differs from GGPL-I in having an additional amino residue (4). Both GGPLs were shown to be species-specific major lipid antigens of M. fermentans (4).Here we describe the structural analysis of a new type of polar lipid isolated from M. fermentans, and we present the complete structural analysis of MfGL-II. 2 Furthermore, we show that both glycolipids of M. fermentans, GGPL-I and GGPL-III, share the basic structure of 6Ј-O-phospho-␣-D-glucopyranosyl-(1Ј33)-1,2-diacyl-glycerol (7) but differ in their polar head groups. MATERIALS AND METHODS Growth of the Organism-Cultures of M. fermentans strain PG18and strain Incognitus (provided by S.-C. Lo, Armed Forces Institute of Pathology, Washington, D.C.) were grown in a modified Channock medium (8) inoculated with a 48-h culture at an inoculum level of 2% and incubated statically at 37°C. After 68 h the cells were harvested, washed twice, and freeze-dried as described previously (8) with yields ranging from 130 to 160 mg dry weight per liter of medium.Lipid Extraction and Purification-Freeze-dried cells were suspended in 25 mM Tris/HCl, pH 7.5, containing 0.25 M NaCl to a final concentration of 25 mg of cells per ml. Lipids were extracted from cell suspensions by the method of Bligh and Dyer (9) and concentrated to near dryness on a rotary evaporator. Quantitative separation of MfGL-II was achieved by silica gel colu...

The physico‐chemical characteristics of the phosphocholine‐containing glycoglycerolipid MfGL‐II govern the permeability properties of Mycoplasma fermentans

“…Deutch et al [6] isolated an unusual choline-containing phosphoglycolipid from the cell membranes of M. fermentans strain PG18 and suggested that this lipid was capable of enhancing the fusion of small, unilamellar vesicles with MOLT-3 lymphocytes in a dose-dependent manner. Structural analysis of this lipid [7] revealed that it is 6 H -O-(3 HH -phosphocholine-2 HH -amino-1 HH -phospho-1 HH ,3 HH -propanediol)-a-dglucopyranosyl-(1 H 33)-1,2-diacylglycerol (MfGL-II). It is present in two forms, a major dipalmitoyl form of M r 1049.5, and a minor stearoyl-palmitoyl form of M r 1077.3 [7].…”

“…Structural analysis of this lipid [7] revealed that it is 6 H -O-(3 HH -phosphocholine-2 HH -amino-1 HH -phospho-1 HH ,3 HH -propanediol)-a-dglucopyranosyl-(1 H 33)-1,2-diacylglycerol (MfGL-II). It is present in two forms, a major dipalmitoyl form of M r 1049.5, and a minor stearoyl-palmitoyl form of M r 1077.3 [7].In the present study we report that an increase in the fraction of MfGL-II occurs upon aging of M. fermentans cultures, and that this increase is accompanied by changes in the permeability and osmotic fragility of the cells. We also show that aged M. fermentans cells are shedding MfGL-II into the suspending medium, a process that is facilitated by EDTA and inhibited by CaCl 2 .…”

“…Structural analysis of this lipid [7] revealed that it is 6 H -O-(3 HH -phosphocholine-2 HH -amino-1 HH -phospho-1 HH ,3 HH -propanediol)-a-dglucopyranosyl-(1 H 33)-1,2-diacylglycerol (MfGL-II). It is present in two forms, a major dipalmitoyl form of M r 1049.5, and a minor stearoyl-palmitoyl form of M r 1077.3 [7].…”

“…Deutch et al [6] isolated an unusual choline-containing phosphoglycolipid from the cell membranes of M. fermentans strain PG18 and suggested that this lipid was capable of enhancing the fusion of small, unilamellar vesicles with MOLT-3 lymphocytes in a dose-dependent manner. Structural analysis of this lipid [7] …”

“…It is present in two forms, a major dipalmitoyl form of M r 1049.5, and a minor stearoyl-palmitoyl form of M r 1077.3 [7].…”