Ca2+ transport through lipid membrane by diastereomer cyclic octapeptides.
Effects of the nature and orientation of a side chain in cyclic octapeptides on Ca2+ transport were examined by using cyclo[L-Lys(Z)-Sar-L-Leu-Sar]2 (C8-L), cyclo[L-Lys(Z)-Sar]4 (C8KS), and their diastereomer cyclic octapeptides, cyclo[L-Lys(Z)-Sar-D-Leu-Sar]2 (C8-D) and cyclo[L-Lys(Z)-Sar-D-Lys(Z)-Sar]2 (C8Kk). All these cyclic octapeptides were found to take a single conformation in CDCl3, and the conformation was C2-symmetric for C8-L and C8-D, and C4-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 greater than C8-D greater than C8-L.
S
S
Kimura
E
E
Ozeki
Y
Y
Imanishi
D015060:1,2-Dipalmitoylphosphatidylcholine; D000595:Amino Acid Sequence; D002118:Calcium; D008081:Liposomes; D008962:Models, Theoretical; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000138:chemical synthesis; D010456:Peptides, Cyclic / Q000138:chemical synthesis; D011487:Protein Conformation
D008081:Liposomes; D009842:Oligopeptides; D010456:Peptides, Cyclic; D015060:1,2-Dipalmitoylphosphatidylcholine; D002118:Calcium