DISRUPTION OF THE GENE ENCODING THE ACYL-COA-BINDING PROTEIN (ACB1) PERTURBS ACYL-COA METABOLISM IN SACCHAROMYCES-CEREVISIAE

The ACB1 gene encoding the acyl-CoA-binding protein (ACBP) was disrupt ed in Saccharomyces cerevisiae. The disruption did not affect the grow th rate on glucose but reduced the growth rate on ethanol slightly. Al though the growth rate of the acb1-disrupted cells was unaffected or o nly slightly affected, the acb1-disrupted strain was unable to compete with wild type cells when grown in mixed culture. The acyl-CoA level in the disrupted cells was increased from 1.5- to 2.5-fold during expo nential growth. The increase in the acyl-CoA level was caused solely b y an increase in de novo synthesized stearoyl-CoA. Experiments with pu rified yeast fatty acid synthetase show that it will synthesize long c hain acyl-CoAs in the absence of acyl-CoA-binding protein. The additio n of ACBP to the incubation medium resulted in a dramatic decrease in the chain length of the synthesized acyl-CoA esters. Despite the fact that the stearoyl-CoA concentration was increased 7-fold and the Delta 9-desaturase mRNA level was increased 3-fold, the synthesis of oleic acid was unchanged in the acb1-disrupted strain. The results strongly indicate that ACBP in yeast is involved in the transport of newly synt hesized acyl-CoA esters from the fatty acid synthetase to acyl-CoA-con suming processes.