YEAST ACYL-COA-BINDING PROTEIN - ACYL-COA-BINDING AFFINITY AND EFFECTON INTRACELLULAR ACYL-COA POOL SIZE

Acyl-CoA-binding protein (ACBP) is a 10 kDa protein characterized in v ertebrates. We have isolated two ACBP homologues from the yeast Saccha romyces carlsbergensis, named yeast ACBP types 1 and 2. Both proteins contain 86 amino acid residues and are identical except for four conse rvative substitutions. In comparison with human ACBP, yeast ACBPs exhi bit 48 % (type 1) and 49 % (type 2) conservation of amino acid residue s. The amino acid sequence of S. carlsbergensis ACBP type 1 was found to be identical with the one ACBP present in Saccharomyces cerevisiae. A recombinant form of this protein was expressed in Escherichia coli and S. cerevisiae, purified, and its acyl-CoA-binding properties were characterized by isoelectric focusing and microcalorimetric analyses. The yeast ACBP was found to bind acyl-CoA esters with high affinity (K -d 0.55 x 10(-10) M). Overexpression of yeast ACBP in S. cerevisiae re sulted in a significant expansion of the intracellular acyl-CoA pool. Finally, Southern-blotting analysis of the two genes encoding ACBP typ es 1 and 2 in S. carlsbergensis strongly indicated that this species i s a hybrid between S. cerevisiae and Saccharomyces monacensis.