Comparison of α-helix stability in peptides having a negatively or positively charged residue block attached either to the N- or C-terminus of an α-helix: The electrostatic contribution and anisotropic stability of the α-helix
✍ Scribed by Sho Takahashi; Eui-Ho Kim; Takeshi Hibino; Tatsuo Ooi
- Publisher
- Wiley (John Wiley & Sons)
- Year
- 1989
- Tongue
- English
- Weight
- 771 KB
- Volume
- 28
- Category
- Article
- ISSN
- 0006-3525
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✦ Synopsis
Synopsis
An estimation of the thermodynamic effects of a charged random coil, which is attached either to the Nor C-terminus of polyalanine, upon a-helix stability is attempted. A temperature induced helix-coil transition of Ala,Lys,Phe and Lys,Ala,Phe was studied under various conditions of salt concentration and pH. By combining the results with previous ones for Ala,Glu,Phe and Glu,Ala,Phe, which have opposite electric charges to the present system [S. Ihara et al. (1982) Bwpolymers 21, 131-1451, the free energy of the coil to helix transition of the polyalanine block could be separated into two terms-one term for the electrostatic interaction of electric charges in the random-coil block with the a-helix dipole, and a second term for the intrinsic stability of the helix. The first term indicates the significance of the helix dipole-charge interactions, which affects the helix stability depending on the attaching side of the charged block and on the sign of the chargca. This clearly shows the anisotropic stability of the a-helix. Furthermore, analysis of the dependence of these thermodynamic quantities on salt concentrations showed, assuming that the effect of the attached electric chafges was symmetric (in other words, the absolute values of the electrostatic interaction terms were independent of the sign of electric charges), that the intrinsic stability of the a-helix was dependent on which side of the helix was attached to the random coil: a random coil attached to the N-terminus of the a-helix had little effect while that attached to a C-terminal significantly destabilized the helix.