Author
P. D. Boyer
Bio: P. D. Boyer is an academic researcher. The author has an hindex of 1, co-authored 1 publications receiving 1635 citations.
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TL;DR: The isolation of the factor responsible for the earlier development of the incisors and eyelids is reported here, a heat-stable, nondialysable, antigenic protein, whose most distinctive chemical characteristic is the absence of phenylalanine and lysine.
2,109 citations
1,654 citations
TL;DR: The results indicate that this enzyme is probably identical to cyclophilin, a recently discovered mammalian protein which binds tightly to cyclosporin A (CsA), which is thought to be linked to the immunosuppressive action of CsA.
Abstract: The enzyme peptidyl-prolyl cis-trans isomerase (PPIase) was recently discovered in mammalian tissues and purified from porcine kidney. It catalyses the slow cis-trans isomerization of proline peptide (Xaa-Pro) bonds in oligopeptides and accelerates slow, rate-limiting steps in the folding of several proteins. Here, we report the N-terminal sequence of PPIase together with further chemical and enzymatic properties. The results indicate that this enzyme is probably identical to cyclophilin, a recently discovered mammalian protein which binds tightly to cyclosporin A (CsA). Cyclophilin is thought to be linked to the immunosuppressive action of CsA. The first 38 amino-acid residues of porcine PPIase and of bovine cyclophilin are identical and the two proteins both have a relative molecular mass of about 17,000 (ref. 7). The catalysis of prolyl isomerization in oligopeptides and of protein folding by PPIase are strongly inhibited in the presence of low levels of CsA. The activities of both PPIase and cyclophilin depend on a single sulphydryl group. At present it is unknown whether the inhibition of prolyl isomerase activity is related with the immunosuppressive action of CsA.
1,310 citations
881 citations
621 citations