Thermodynamics of glycophorin A transmembrane helix dimerization in C14 betaine micelles |
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Authors: | Fleming Karen G Ren Cha-Chi Doura Abigail K Eisley Matthew E Kobus Felix J Stanley Ann Marie |
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Institution: | T.C. Jenkins Department of Biophysics, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218, USA. karen.fleming@jhu.edu |
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Abstract: | We have used sedimentation equilibrium analytical ultracentrifugation to measure the free energy change for the glycophorin A transmembrane helix-helix dimerization in C14 betaine micelles. By varying the amount of micellar C14 betaine, we show that the protein association reaction in the micellar C14 phase behaves as an ideal-dilute solution. In this hydrophobic environment, the mole-fraction standard state free energy change for self-association of the SNGpA99 glycophorin A construct is -5.7 (+/-0.3, N=5) kcal mol(-1) at 25 degrees C. Compared with previous results carried out in C(8)E(5) micellar solutions, the free energy of dimerization is 1.3 kcal mol(-1) less favorable in C14 betaine micelles. In contrast, when considered on a per-interface basis, the formation of the glycophorin A transmembrane dimer in C14 betaine micelles may be more favorable than the association of several designed transmembrane peptides. |
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