13C Nuclear magnetic resonance study of salt induced conformational change of basic polypeptides: Poly (L-lysine), poly (L-arginine), and poly (L-ornithine)

✍ Scribed by Hazime Saitô; Toyokazu Ohki; Masahiko Kodama; Chikayoshi Nagata

• Publisher: Wiley (John Wiley & Sons)
• Year: 1978
• Tongue: English
• Weight: 553 KB
• Volume: 17
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.1978.360171107

✦ Synopsis

ku, Tokyo, J a p a n 104

Synopsis

A I3C-nmr study of the salt-induced helix-coil transition of the basic polypeptides poly(L-lysine) [(Lys),], poly(i-arginine) [(Arg),], and poly(i-ornithine) [(Orn),] was performed to serve as a reference of the helical portion of histones and other proteins. As is the case with pH-induced helixxoil transition, the downfield displacement of the C" and carbonyl carbon signals are observed in the helical state. The upfield shift of the CB signals, on the other hand, is noted in the salt-induced transition. Regardless of the differences in the side chains and also the salts used, very similar helix-induced chemical shifts are obtained for (Lys), and (Arg),. However, the displacement of the Ca, Co, and carbonyl carbons of (Om), in the presence of 4M NaC104 is found to be almost 50% of that of (Lys), and (Arg),. This is explained by the fact that the maximum helical content is about 5W?, consistent with the ORD result. Further, the motion of the backbone and side chains of the helical form was estimated by measuring the spin-lattice relaxation time (TI), nuclear Overhauser enhancement (NOE), and line width. In the case of (Lys),, the motion of the side chains is changed very little in comparison with that of the random coil, indicating that the aggregation of the salt-induced helix is small in contrast to that of the pH-induced helix. For (Arg),, however, the precipitate of the helical polymers is mainly due to aggregation.