title: Thermodynamics of glycophorin A transmembrane helix dimerization in C14 betaine micelles.
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.
authors.affiliation: T.C. Jenkins Department of Biophysics, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218, USA. karen.fleming@jhu.edu
authors.forename: Karen G
authors.initials: KG
authors.lastname: Fleming
authors.forename: Cha-Chi
authors.initials: CC
authors.lastname: Ren
authors.forename: Abigail K
authors.initials: AK
authors.lastname: Doura
authors.forename: Matthew E
authors.initials: ME
authors.lastname: Eisley
authors.forename: Felix J
authors.initials: FJ
authors.lastname: Kobus
authors.forename: Ann Marie
authors.initials: AM
authors.lastname: Stanley
mesh_terms: D001622:Betaine / Q000737:chemistry; D002247:Carbon Isotopes; D002462:Cell Membrane / Q000737:chemistry*; D019281:Dimerization; D006021:Glycophorins / Q000737:chemistry*; D008565:Membrane Proteins / Q000737:chemistry*; D008823:Micelles; D017433:Protein Structure, Secondary; D013816:Thermodynamics; D014461:Ultracentrifugation / Q000379:methods
chemical_list: D002247:Carbon Isotopes; D006021:Glycophorins; D008565:Membrane Proteins; D008823:Micelles; D001622:Betaine