Helix bundles and coiled coils in α-spectrin and tropomyosin: A theoretical CD study

✍ Scribed by Kimberly A. Bode; Jon Applequist

• Publisher: Wiley (John Wiley & Sons)
• Year: 1997
• Tongue: English
• Weight: 83 KB
• Volume: 42
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/(sici)1097-0282(199712)42:7<855::aid-bip10>3.0.co;2-8

✦ Synopsis

The dipole interaction model is used to investigate the effects of interactions between helices and supertwisting of helices by determining whether the predicted UV absorption and CD spectra for the three-helix bundle and coiled coil are significantly different from spectra for the single straight a-helix. Crystallographic data by Yan et al. for a-spectrin are used to construct a three-helix bundle of poly(L-alanine) modeling the protein. Backbone torsion angles represented by Fourier series are used to generate supertwisted helices and coiled coil models of poly(L-alanine) that have pitch, radius, and residue repeat similar to experimental crystallographic data on tropomyosin. Calculated CD spectra are compared with available experimental data. Theoretical spectra for the three-helix bundle and the supertwisted structures are quite similar to predictions for the straight a-helix of the same length with similar torsion angles, suggesting that CD is primarily dependent on the average backbone conformation and would not be a sensitive tool for distinguishing between single straight helices and closely packed or twisted a-helices.