Anglysis of novel gevefor proline analogue resistance found in budding yesst Σ12786

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We recently have discovered, on the chromosome of the budding yeast Saccharmyces cerevisiae Σ1278b, a novel gene MPR1 (sigma 1278b gene for L-proline-analogue resistance) required for the resistance of Σ1278 backgraound strains to toxic AZC.1. The genes MPR1 and MPR2, both characterized by one amino acid change at position 85, were present on chromosomes XIV and X of Σ1278b background strains, respectively, but were absent in the S. cerevisiae S288C used for the genomic sequence determination.2. Gene expression in Escherichia coli and enzymatic analysis showed that MPR1 encodes a novel AZC acetyltransferase, by which L-proline itself and other L-proline analogues are not acetylated. The MPR1-encoded protein (Mprlp) was considered to be a member of the N-acetyltansferase superfamily. We believe that AZC is converted to N-acetyl AZC by Mprlp in the cytoplasm, and consequently, N-acetyl AZC no longer replaces L-proline during the biosynthesis of protein.3. By the comparative analysis of MPR1 in the S. cerevisiae complex species, the type strain of S. paradoxus exhibited resistance and acetyltransferase activity to AZC. The new MPR1 homologue (Spa MPR1) from S. paradoxus was isolated by PCR with the primers based on the sequence of MPR1. Gene expression and enzymatic analysis showed that the cloned Spa MPR1 encodes an AZC acetyltransferase, which has 87% identity to Mprlp.4. The amino acid sequence of the predicted Mprlp was homologous to that of the fission yeast Schizosaccharomyces pombe hypothetical 23.8 kDa protein. We analyzed the S. pombe homologue of MPR1, ppr1^+ (pombe MPR1). This gene was responsibel to the AZC resistance of S. pombe and encodes an acetyltransferase that detoxifies AZC in a manner similar to that by MPR1.Our findings here suggest that this enzyme may have a physiologically conserved function additional to that of detoxifying unusual imino acid AZC.