Protein S-myristoylation in Leishmania revealed with a heterologous reporter

Reversible esterification of myristic acid to cysteine residue(s) (S-myrist oylation) was documented recently in the protozoan Trypanosoma brucei. Unli ke N-myristoylation, S-myristoylation appears to be rare (or non-existent) in animal cells and has not been documented in any other trypanosome. Reaso ning that a lack. of knowledge of appropriate substrates may have contribut ed to this state of affairs, we devised an assay to test for protein S-myri stoylation in the ancient eukaryote Leishmania. A cDNA encoding a glycosylp hosphatidylinositol-phospholipase C (GPI-PLC) from T. brucei was transfecte d into Leishmania and the expressed protein analyzed for covalent lipid mod ifications. Leishmania modified the reporter with myristate in a thio-ester linkage. From these observations, we infer that (i) GPI-PLC may be used as a reporter of this lipid modification in eukaryotes, and (ii) protein S-my ristoylation might have ancient origins. (C) 1999 Academic Press.