2 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 synthas e, we searched the genome of Saccharomyces cerevisiae for sequences th at are homologous to conserved regions of bacterial fatty acid synthas e genes. We found the gene products of ORF YKL055c (EMBL Accession No. X75781) and of YOR221C (EMBL Accession No. X92441) to be homologous t o bacterial 3-oxoacyl-(acyl carrier protein) reductases and to malonyl -CoA:ACP-transferases, respectively. We disrupted these two genes whic h in both cases led to a respiratory deficient phenotype, as is the ca se for the genes encoding a mitochondrial acyl carrier protein and a b eta-ketoacyl-ACP synthase. We propose to call the above mentioned gene s OAR1 [3-oxo-acyl-(acyl carrier protein) reductase] and MCT1 (malonyl -CoA:ACP transferase). They are presumed to be part of a type-II mitoc hondrial fatty acid synthase, a relic of the endosymbiontic origin of mitochondria, delivering substrates for phospholipid re-modelling and/ or repair.