S-myristoylation of a glycosylphosphatidylinositol-specific phospholipase C in Trypanosoma brucei

Covalent modification with lipid can target cytosolic proteins to biologica l membranes. With intrinsic membrane proteins, the role of acylation can be elusive. Herein, we describe covalent lipid modification of an integral me mbrane glycosylphosphatidylinositol-specific phospholipase C (GPI-PLC) from the kinetoplastid Trypanosoma brucei. Myristic acid was detected on cystei ne residue(s) (i.e. thiomyristoylation). Thiomyristoylation occurred both c o- and post-translationally Acylated GPI-PLC was active against variant sur face glycoprotein (VSG). The half-life of fatty acid on GPI-PLC was 45 min, signifying the dynamic nature of the modification. Deacylation in vitro de creased activity of GPI-PLC 18-30-fold. Thioacylation, from kinetic analysi s, activated GPI-PLC by accelerating the conversion of a GPI-PLC VSG comple x to product. Reversible thioacylation is a novel mechanism for regulating the activity of a phospholipase C.