Extracellular phosphorylation in the parasite, Leishmania major

David S. Lester*, Thomas Hermoso, Charles L. Jaffe

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

28 Scopus citations

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 languageEnglish
Pages (from-to)293-298
Number of pages6
JournalBiochimica et Biophysica Acta - Molecular Cell Research
Volume1052
Issue number2
DOIs
StatePublished - 2 May 1990
Externally publishedYes

Keywords

  • (L. major)
  • Exometabolite
  • Phosphorylation
  • Protein kinase

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