A novel peptidyl‐prolyl cisltrans isomerase from Escherichia coli

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Abstract
A novel peptidyl-prolyl cis/trans isomerase was isolated from Escherichia coli cell extract and characterized partially. Determination of the molecular mass by electrospray mass spectrometry indicated a protein of 10102 ± 2 Da, smaller than cyclophilins or FK506 binding proteins currently known. The specificity constant k cat / K m determined with Succinyl-Ala-Xaa-Pro-Phe-4-nitroanilide (Xaa = Leu) had a value comparable to those from cyclophilins from the same organism. However, the pattern of subsite specificity (Xaa = Gly, Ala, Val, Ile, Leu, Phe, Trp, His, Lys and Glu) was reminiscent of FK506 binding peptidyl-prolyl cis/trans isomerases. The enzyme activity was not inhibited by cyclosporin A or FK506 at inhibitor concentrations of < 5 μM, concentrations that affect most bacterial peptidyl-prolyl cis/trans isomerases. Computer-assisted analysis of 21 amino acid residues of the N-terminus determined by Edman degradation revealed no homology to known peptidyl-prolyl cis/trans isomerases.