Copper ion complex formation of polypeptide containing side-chain pyridyl groups

✍ Scribed by Yoshitomo Nagata; Satoru Kanuka; Takatoshi Kinoshita; Akira Takizawa; Yoshiharu Tsujita; Hiroaki Yoshimizu

• Publisher: Wiley (John Wiley & Sons)
• Year: 1994
• Tongue: English
• Weight: 508 KB
• Volume: 34
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.360340603

✦ Synopsis

The complex formation behaviors of an a-helical polypeptide containing pyridyl ligands in the side chains, poly (N"-2-pyridylmethyl L-glutamine) (PBPG) , were investigated by absorption and CD spectroscopy using Cu2+ ion as a guest molecule in 2,2,2-trifluoroethanol solution. In the low Cu2+ ion concentration, P2PG exhibited the predominant formation of Cu2+ and two pyridyl side-chain complexes, involving a regular arrangement of the pyridyl side chains. On the other hand, the complexes were converted to Cuz+ and one pyridyl side-chain species with increasing Cu2+ ion concentration. The conversion was accompanied by the disappearance of the side-chain ordered structure without any changes in the backbone conformation. Moreover, the still remaining coordination sites of Cu2+ were capable of complexing monomer pyridine (Py ) added as a second guest to form ternary complexes, P2PG-Cu2+-Py, following the reconstitution of the ordered structure on the periphery of the a-helix backbone. The unique characteristi.cs of P2PG can be explained in terms of the restriction of the pyridyl side chains to form intramolecular chelate complexes, depending on the rigid a-helix conformation.