title: Release of ecto-protein kinases by the protozoan parasite Leishmania major.
abstract: Leishmania major promastigotes have externally oriented ecto-protein kinases (PK) that are capable of phosphorylating both endogenous membrane substrates and foreign proteins. Live parasites phosphorylate protamine sulfate, casein, and phosvitin but not bovine serum albumin. Addition of exogenous PK substrates, such as phosvitin or casein, induced the shedding of ecto-PK that are capable of phosphorylating protamine sulfate. No phosphorylation of protamine sulfate was seen when cell-free supernatants from promastigotes incubated with either buffer alone or bovine serum albumin were used. A second enzyme, a constitutively released PK that phosphorylates casein or phosvitin and not protamine sulfate or mixed histones, was identified and characterized. This PK is inhibited by 5 microM staurosporine, 50 microg/ml heparin, and 75 microM CKI-7, concentrations typical of the IC50 found for other eukaryotic casein kinases (CK). The constitutively shed ecto-PK specifically phosphorylated a peptide substrate for CK1 but not for CK2, suggesting that this shed PK is similar to CK1.
authors.affiliation: Department of Parasitology, The Kuvin Centre for the Study of Infectious and Tropical Diseases, Hebrew University-Hadassah Medical School, P. O. Box 12272, Jerusalem 91120, Israel.
authors.forename: N
authors.initials: N
authors.lastname: Sacerdoti-Sierra
authors.forename: C L
authors.initials: CL
authors.lastname: Jaffe
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D047388:Casein Kinases; D002417:Cattle; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006493:Heparin / Q000494:pharmacology; D006790:Host-Parasite Interactions; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000378:metabolism; D007546:Isoquinolines / Q000494:pharmacology; D018320:Leishmania major / Q000201:enzymology* / Q000502:physiology; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011479:Protamines / Q000378:metabolism; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases / Q000378:metabolism*; D019311:Staurosporine / Q000494:pharmacology; D013379:Substrate Specificity; D013449:Sulfonamides / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D007527:Isoenzymes; D007546:Isoquinolines; D011479:Protamines; D047428:Protein Kinase Inhibitors; D013449:Sulfonamides; C058815:N-(2-aminoethyl)-5-chloroisoquinoline-8-sulfonamide; C017967:W 7; D006493:Heparin; D011494:Protein Kinases; C034454:ectoprotein kinase; D047388:Casein Kinases; D019311:Staurosporine