Altered Membrane Association and Complex Formation of Tafazzin in the Absence of Cardiolipin

Nascent cardiolipin (CL) is remodeled through a series of deacylation:reacylation cycles to obtain its “mature” fatty acyl chain constituents. Tafazzin (Taz1p), the mutant gene product associated with Barth syndrome patients, is hypothesized to act as the/a monolysoCL acyltransferase mediating CL remodeling. Based on this hypothesized function, we sought to determine the effect, if any, on the expression, localization, membrane association, and complex assembly of Taz1p expressed in a yeast strain harboring a deletion of the cardiolipin synthase gene (Δ crd1 ). In the absence of its putative target phospholipid, CL, Taz1p expression is unaffected. In the Δ crd1 mitochondria, Taz1p remains anchored to mitochondrial membranes as an integral interfacial membrane protein. However, curiously, in the absence of CL, Taz1p is significantly and uniquely less extractable by 0.1M carbonate pH 11.5 relative to wildtype mitochondria. Comparison of Taz1p complex formation, as assessed by both 1D blue‐native (BN) and 2D BN/SDS‐PAGE indicates that in the absence of CL, 1–2 large complexes are missing, whereas a smaller complex and a broad smear, presumably reflecting associated phospholipids, are still observed. Thus, while the gross expression and subcellular localization of Taz1p are not altered in the absence of its putative target lipid, CL, the ability of Taz1p to form some macromolecular structures is lost in the absence of CL. These studies suggest that the lipid environment may be critical for Taz1p function. This work was supported by NIH grants: GM 45952 and GM 61721