Two genes of the putative mitochondrial fatty acid synthase in the genome of Saccharomyces cerevisiae.

In order to find further genes of the mitochondrial fatty acid synthase, we searched the genome of Saccharomyces cerevisiae for sequences that are homologous to conserved regions of bacterial fatty acid synthase genes. We found the gene products of ORF YKL055c (EMBL Accession No. X75781) and of YOR221C (EMBL Accession No. X92441) to be homologous to bacterial 3-oxoacyl-(acyl carrier protein) reductases and to malonyl-CoA:ACP-transferases, respectively. We disrupted these two genes which in both cases led to a respiratory deficient phenotype, as is the case for the genes encoding a mitochondrial acyl carrier protein and a beta-ketoacyl-ACP synthase. We propose to call the above mentioned genes OAR1 [3-oxo-acyl-(acyl carrier protein) reductase] and MCT1 (malonyl-CoA:ACP transferase). They are presumed to be part of a type-II mitochondrial fatty acid synthase, a relic of the endosymbiontic origin of mitochondria, delivering substrates for phospholipid re-modelling and/or repair.