Ca2+ transport through lipid membrane by diastereomer cyclic octapeptides

✍ Scribed by Shunsaku Kimura; Eiichi Ozeki; Yukio Imanishi

• Publisher: Wiley (John Wiley & Sons)
• Year: 1989
• Tongue: English
• Weight: 537 KB
• Volume: 28
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.360280706

✦ Synopsis

Effects of the nature and orientation of a side chain in cyclic octapeptides on Ca" transport were examined by using cycld~-Lys(Z)-Sar-~-Leu-Sar], (C8-L), cyclo[~-Lys(Z)-Sar], (C8KS), and their diastereomer cyclic octapeptides, c y c ~o [ L -~y s ( ~) -~a r -D -~u -~a r ] ,

(C8-D) and CYC~~L-LYS(Z)sar-D-Lys(Z)-sar], (C8Kk). All these cyclic octapeptides were found to take a single conformation in CDCl,, and the conformation was C,-symmetric for C8-L and C8-D, and C,-symmetric for C8KS and C8Kk. They formed a complex with Ca2+. Upon complexation, C8KS accompanied isomerization of peptide bonds, but C8-D retained the arrangement of peptide bonds. The amount of Ca2+ extracted from an aqueous solution to a chloroform solution by all L cyclic octapeptide C8-L or C8KS was about twice that of Na+, but 6 -8-fold smaller than that by C8-D or C8Kk including D units. These cyclic octapeptides were capable of transporting Ca2+ through a lipid membrane above the phase transition temperature, and the transport rate decreased in the order of C8Kk C8KS > C8-D > C8-L.