The thermal denaturation of nonpolymerizable alpha alpha-tropomyosin and its segments as a function of ionic strength

Biopolymers
J M MoA Holtzer

Abstract

Nonpolymerizable tropomyosin (NPTm) is found to unfold thermally at high ionic strength almost exactly as the parent protein, but it does not aggregate at low ionic strength. Thus, NPTm can be used as a tropomyosin surrogate whose coiled-coil structural stability can be probed by varying the ionic strength. Studies of NPTm by CD show that increasing ionic strength stabilizes the coiled-coil structure. CD spectra over a wide range of helix content, obtained by varying either temperature or ionic strength, show an isodichroic point at 203 nm, suggesting a local, residue-level, two-state model. At given temperature, such a local helix in equilibrium random equilibrium suggests ln [phi h/(1-phi h)] = A1 + A2In, wherein phi h is the fraction helix, and A1, A2, and n are constants. In the low ionic strength region, theoretical limiting laws for ionic strength mediated charge-charge, dipole-dipole, and apolar-apolar (salting out) interactions give, respectively, n = 0.5, 1.0, and 1.0. Our experimental values for 40 degrees C, where the data span a wide range of helix content, show n = 1.0, suggesting that ionic strength stabilizes either by reducing dipole-dipole repulsions or by enhancing hydrophobic interactions, both probably inter...Continue Reading

References

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Citations

May 1, 1997·Journal of Peptide Science : an Official Publication of the European Peptide Society·W D KohnR S Hodges
Jan 1, 1995·Biopolymers·M E HoltzerA Holtzer
Aug 1, 1993·Protein Science : a Publication of the Protein Society·N J Greenfield, S E Hitchcock-DeGregori
Feb 1, 1991·Proceedings of the National Academy of Sciences of the United States of America·J M MoA Holtzer
Apr 15, 1994·European Journal of Biochemistry·Y Ishii
Mar 13, 2009·Biopolymers·Fernando CorrêaRoberto K Salinas
Sep 2, 1998·Journal of Structural Biology·S S Lehrer, A Yuan
Aug 9, 2002·The Journal of Biological Chemistry·Adriana A PaulucciChuck S Farah
Aug 14, 2013·Journal of Materials Chemistry. B, Materials for Biology and Medicine·Andrew A WalkerTara D Sutherland
May 10, 1991·Journal of Chromatography·D L Crimmins, M E Holtzer

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