TAILIEUCHUNG - Báo cáo khoa học: Escherichia coli cyclophilin B binds a highly distorted form of trans-prolyl peptide isomer

Cyclophilins facilitate the peptidyl-prolyl isomerization of atrans-isomer to a cis-isomer in the refolding process of unfolded proteins to recover the natural folding state with cis-proline , only short peptideswitha cis-formproline have been observed in complexes of human and Escherichia coliproteins of cyclophilin A, which is present in cytoplasm. The crystal structures analyzed in this study show two complexes inwhich peptides having atrans-form proline, . succinyl-Ala-trans-Pro-Ala-p-nitroanilide and acetyl-Ala-Ala-trans-Pro-Ala-amidomethylcoumarin, are bound on a K163T mutant ofEscherichia colicyclo-philin B, the preprotein of which has a signal sequence | Eur. J. Biochem. 271 3794-3803 2004 FEBS 2004 doi Escherichia coli cyclophilin B binds a highly distorted form of frafls-prolyl peptide isomer Michiko Konno1. Yumi Sano1 Kavoko Okudaira1. Yoko Kawaguchi1 Yoko Yamaaishi-Ohmori1 Shinya Fushinobu2 and Hiroshi Matsuzawa2 1 Department of Chemistry Ochanomizu University Otsuka Bunkyo-ku Tokyo Japan department of Biotechnology The University of Tokyo Yayoi Bunkyo-ku Tokyo Japan Cyclophilins facilitate the peptidyl-prolyl isomerization of a trans-isomer to a cis-isomer in the refolding process of unfolded proteins to recover the natural folding state with cis-proline conformation. To date only short peptides with a cis-form proline have been observed in complexes of human and Escherichia coli proteins of cyclophilin A which is present in cytoplasm. The crystal structures analyzed in this study show two complexes in which peptides having a transform proline . succinyl-Ala-trans-Pro-Ala-p-nitroanilide and acetyl-Ala-Ala-trans-Pro-Ala-amidomethylcoumarin are bound on a K163T mutant of Escherichia coli cyclo-philin B the preprotein of which has a signal sequence. Comparison with cis-form peptides bound to cyclophilin A reveals that in any case the proline ring is inserted into the hydrophobic pocket and a hydrogen bond between CO of Pro and Ng2 of Arg is formed to fix the peptide. On the other hand in the cis-isomer the formation of two hydrogen bonds of NH and CO of Ala preceding Pro with the protein fixes the peptide whereas in the trans-isomer formation of a hydrogen bond between CO preceding Ala-Pro and His47 Ne2 via a mediating water molecule allows the large distortion in the orientation of Ala of Ala-Pro. Although loss of double bond character of the amide bond of Ala-Pro is essential to the isomerization pathway occurring by rotating around its bond these peptides have forms impossible to undergo proton transfer from the guanidyl group of Arg to the prolyl N atom which induces loss .

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