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In a comparative study of housekeeping genes of Pseudomonas aeruginosa and Escherichia coli, the nucleotide sequence of a proline biosynthetic gene, proC, of P. aeruginosa has been determined. The subunit molecular mass (approximately 29 kDa) and the N-terminal amino acid sequence of purified delta 1-pyrroline 5-carboxylate reductase, the proC gene product, were in agreement with the proC nucleotide sequence. A survey of pairs of isofunctional genes from P. aeruginosa and E. coli reveals that within each pair, translated genes (including proC) have diverged more strongly than have untranslated genes specifying ribosomal or transfer RNAs. The translated genes, but not the untranslated ones, have a G + C content that is typical of the respective genomic G + C contents.

Cyclophilin (CPH) has been isolated from the yeast Saccharomyces cerevisiae, purified to homogeneity and partially sequenced. Oligodeoxyribonucleotides deduced from this sequence were used to isolate the corresponding cDNA and gene. An open reading frame coding for a 162-amino acid (aa) protein with a calculated Mr of 17,392, was deduced from the nucleotide sequence. Comparison between yeast and human CPH shows a very high overall sequence conservation (65% aa homology). The binding of yeast CPH to cyclosporin A is identical to that of human and bovine CPH. Unlike in Neurospora crassa, a mitochondrial form of CPH could not be detected in yeast. Southern-blot analysis of yeast DNA shows that only one CPH-related sequence is present per haploid genome, whereas at least 20 genes or pseudogenes were detected in the human and rat genome. Purified yeast CPH exhibits peptidyl-prolyl cis-trans isomerase activity, albeit to a far lesser extent than the mammalian protein.