CONFIRMATION OF THE EXISTENCE OF A 3RD FAMILY AMONG PEPTIDYL-PROLYL CIS TRANS ISOMERASES - AMINO-ACID-SEQUENCE AND RECOMBINANT PRODUCTION OF PARVULIN/

In addition to the major cyclophilin-like peptidyl-prolyl cis/trans is omerases (PPIases) of Escherichia coli an enzyme of very low relative molecular mass (10.1 kDa) was discovered in this organism which gave f irst indication of the existence of a novel family in this enzyme clas s [1994, FEBS Lett. 343, 65-69]. In the present report we describe the chemically determined amino acid sequence of four peptides derived fr om the 10.1 kDa protein by the treatment with either cyanogen bromide or endoproteinase Lys-C. Together with a continuous run of 75 amino ac ids starting N-terminally, the sequence of the mature enzyme, 92 resid ues in length, was elucidated. Cloning and determination of the primar y structure of a DNA fragment encoding this enzyme were also performed . Overexpression of the enzyme by using multicopies of plasmid pSEP38 in E. coli and detecting an enhanced PPIase activity attributed to the 10.1 kDa enzyme provided additional proof that the 92 amino acid prot ein was a PPIase. The enzyme was called parvulin (lat.: parvulus, very small). Homology analyses indicated that several parvulin-like protei ns could be found in the database screened. To further elucidate the f unctional role of PPIases it might be of some importance that homologo us proteins like the PrtM protein of Lactococcus lactis and the PrsA l ipoprotein of Bacillus subtilis are known to be involved in the protei n export and maturation machinery of the bacteria.