Conformation of sequential polypeptides of (Lysi-Leuj), (Lysi-Serj), and (Lys-Gly) in sodium dodecyl sulfate solution

✍ Scribed by Shigeo Kubota; Kiyoshi Ikeda; Jen Tsi Yang

• Publisher: Wiley (John Wiley & Sons)
• Year: 1983
• Tongue: English
• Weight: 805 KB
• Volume: 22
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.360221009

✦ Synopsis

A series of sequential polypeptides (Lys,Rj), (R is Leu, Ser, or Gly) and random copolypeptides, (Lys', Leuy), , were synthesized. Their conformation in NaDodS04 solution was determined by CD. Only (Lys-Leu),, (Lys-Ser),, and (Lysa-Ser), adopt a stable 0-form in the surfactant solution; (Lys-Sern),, (Lys-Sera),, (Lysz-Serz),, and (Lysz-Ser), have an unstable 0-form, which reverts to an unordered form in high NaDodS04 concentrations, even though both Ser and DodS0;-bound Lys+ are 0-formers. In contrast, (Lys-Gly), remains unordered in NaDodS04 solution. On the other hand, Lys-rich (Lysz-Leu), forms an unstable helix and (Lysz-Leuz), a stable helix in NaDodS04 solution. In 25 mM NaDodS04 (Lys", Leuy), also forms a helix up to x = 75 and reverts to the 0-form at x = 90. This compares with the helical conformation of (Lys", Alay), up to x = 65 and its 0-form at x = 90, suggesting that Leu is an even stronger helix-former than Ala. Our results may provide a plausible explanation for the increase in helicity and disruption of the 0-form for many proteins in Na-DodS04 solution, that is, the polypeptide chain of a protein usually favors a helical conformation over a @-form in the presence of excess surfactant.