Ubiquitination of plasma membrane ectophosphatase in bloodstream forms of Trypanosoma brucei.
Bloodstream forms of Trypanosoma brucei contain plasma-membrane-integral acidic ectophosphatase. Here, it is shown by N-terminal sequencing that the ectophosphatase found in ricin-binding material was modified by ubiquitin. Three different ubiquitinated species corresponding to single, double and triple ubiquitinated forms of the enzyme were identified. Immunofluorescence studies with live bloodstream-form parasites showed that the ectophosphatase was localized in the flagellar pocket-the sole site for endocytosis in trypanosomes. As ubiquitin modification of plasma membrane proteins serves as an internalization signal, it is suggested that ubiquitinated ectophosphatase is labelled for endocytosis.
Steverding
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Abteilung Parasitologie, Hygiene-Institut der Ruprecht-Karls-Universtät, Im Neuenheimer Feld 324, 69120 Heidelberg, Germany. dsteverding@hotmail.com
D000135:Acid Phosphatase / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D002462:Cell Membrane / Q000201:enzymology*; D016384:Consensus Sequence; D051379:Mice; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry; D012276:Ricin / Q000378:metabolism; D014346:Trypanosoma brucei brucei / Q000201:enzymology* / Q000254:growth & development; D014452:Ubiquitins / Q000378:metabolism*
D010455:Peptides; D014452:Ubiquitins; D012276:Ricin; D000135:Acid Phosphatase