Abstract
Intact promastigotes or cell-free extracts of the parasite Leishmania major were labelled with adenosine 5′[γ-32P]-triphosphate (ATP). This resulted in the identification of eleven phosphoproteins. [γ-32P]ATP incorporation into endogenous and exogenous substrates was insensitive to most of the commonly used protein kinase inhibitors and activators indicating that the leishmanial enzyme(s) may represent a new class of kinase(s). In addition, exogenous substrate specificity was inconsistent with the preferences of second messenger-dependent protein kinases. Cyclic AMP had differential effects on phosphorylation in intact cells and lysates. The majority of kinase activity could be attributed to an externally oriented membrane-associated protein kinase(s), as no specific cytosolic phosphoproteins were found and intact cells phosphorylated exogenous substrates. Labelled ATP did not cross the membrane and [α-32P]ATP was an unsuitable substrate for the phosphorylation activity. The ectokinase activity on live Leishmania exhibited a different substrate preference when compared to the protein kinase activity in the particulate fraction, suggesting that more than one protein kinase many be present in L. major. Three serine-labelled phosphoproteins were specifically released into the medium. The presence of an ecto-kinase and these released phosphoproteins may play a significant role in host-parasitie interactions.
Original language | English |
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Pages (from-to) | 293-298 |
Number of pages | 6 |
Journal | Biochimica et Biophysica Acta - Molecular Cell Research |
Volume | 1052 |
Issue number | 2 |
DOIs | |
State | Published - 2 May 1990 |
Externally published | Yes |
Keywords
- (L. major)
- Exometabolite
- Phosphorylation
- Protein kinase