Thermodynamics of glycophorin A transmembrane helix dimerization in C14 betaine micelles

Biophys Chem 108(1-3):7 (2004) PMID 15043920

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) kcalmol^-^1 at 25 ^oC. Compared with previous results carried out in C"8E"5 micellar solutions, the free energy of dimerization is 1.3 kcalmol^-^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.