Proteophosphoglycans of Leishmania mexicana. Identification, purification, structural and ultrastructural characterization of the secreted promastigote proteophosphoglycan pPPG2, a stage-specific glycoisoform of amastigote aPPG.
Protozoan parasites of the genus Leishmania secrete a range of proteophosphoglycans that appear to be important for successful colonization of the sandfly and for virulence in the mammalian host. A hallmark of these molecules is extensive phosphoglycosylation by phosphoglycan chains via the unusual linkage Manalpha1-PO(4)-Ser. In this study we have identified and purified to apparent homogeneity a novel proteophosphoglycan (pPPG2) which is secreted by Leishmania mexicana promastigotes (sandfly stage). Amino acid analysis and immunoblots using polypeptide-specific antisera suggest that pPPG2 shares a common protein backbone with a proteophosphoglycan (aPPG) secreted by Leishmania mexicana amastigotes (mammalian stage). Both pPPG2 and aPPG show a similar degree of Ser phosphoglycosylation (50. 5 mol% vs. 44.6 mol%), but the structure of their phosphoglycan chains is developmentally regulated: in contrast to aPPG which displays unique, complex and highly branched glycan chains [Ilg, Craik, Currie, Multhaup, and Bacic (1998) J. Biol. Chem. 273, 13509-13523], pPPG2 contains short unbranched structures consisting of >60 mol% neutral glycans, most likely (Manalpha1-2)(0-5)Man and Galbeta1-4Man, as well as about 40 mol% monophosphorylated glycans of the proposed structures PO(4)-6Galbeta1-4Man and PO(4)-6(Glcbeta1-3)Galbeta1-4Man. The major differences between pPPG2 and aPPG with respect to their apparent molecular mass, their ultrastructure and their proteinase sensitivity are most likely a consequence of this stage-specific glycosylation of their common protein backbone.
Klein
C
C
Max-Planck-Institut für Biologie, Abteilung Membranbiochemie Corrensstrasse 38, D-72076 Tübingen, Germany.
Göpfert
U
U
Goehring
N
N
Stierhof
Y D
YD
Ilg
T
T
D000596:Amino Acids / Q000032:analysis; D000818:Animals; D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D002851:Chromatography, High Pressure Liquid; D015801:Helminth Proteins; D007894:Leishmania mexicana / Q000737:chemistry*; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D019606:Phosphoamino Acids / Q000032:analysis; D011134:Polysaccharides / Q000737:chemistry; D011509:Proteoglycans / Q000737:chemistry* / Q000302:isolation & purification; D015800:Protozoan Proteins / Q000737:chemistry* / Q000302:isolation & purification
D000596:Amino Acids; D015801:Helminth Proteins; D019606:Phosphoamino Acids; D011134:Polysaccharides; C405069:Ppg2 protein, Leishmania mexicana; D011509:Proteoglycans; D015800:Protozoan Proteins