The Stability of Transmembrane Helix Interactions Measured in a Biological Membrane

• Published in: Journal of molecular biology 2006-05, Vol.358 (5), p.1221-1228
• Main Authors: Finger, Carmen, Volkmer, Thomas, Prodöhl, Alexander, Otzen, Daniel E., Engelman, Donald M., Schneider, Dirk
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Amino Acid Substitution; Bacterial Proteins - chemistry; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Dimerization; Drug Stability; Escherichia coli - genetics; Escherichia coli - metabolism; Escherichia coli Proteins - chemistry; Escherichia coli Proteins - genetics; Escherichia coli Proteins - metabolism; GALLEX; membrane protein folding; Membrane Proteins - chemistry; Membrane Proteins - genetics; Protein Structure, Secondary; Recombinant Proteins - chemistry; Recombinant Proteins - genetics; Recombinant Proteins - metabolism; Serine Endopeptidases - chemistry; Serine Endopeptidases - genetics; Serine Endopeptidases - metabolism; stability; Thermodynamics; transmembrane helix; Δ G, dimerization
• ISSN: 0022-2836; 1089-8638
• DOI: 10.1016/j.jmb.2006.02.065

Despite some promising progress in the understanding of membrane protein folding and assembly, there is little experimental information regarding the thermodynamic stability of transmembrane helix interactions and even less on the stability of transmembrane helix–helix interactions in a biological membrane. Here we describe an approach that allows quantitative measurement of transmembrane helix interactions in a biological membrane, and calculation of changes in the interaction free energy resulting from substitution of single amino acids. Dimerization of several variants of the glycophorin A transmembrane domain are characterized and compared to the wild-type (wt) glycophorin A transmembrane helix dimerization. The calculated ΔΔ G app values are further compared with values found in the literature. In addition, we compare interactions between the wt glycophorin A transmembrane domain and helices in which critical glycine residues are replaced by alanine or serine, respectively. The data demonstrate that replacement of the glycine residues by serine is less destabilizing than replacement by alanine with a ΔΔ G app value of about 0.4 kcal/mol. Our study comprises the first measurement of a transmembrane helix interaction in a biological membrane, and we are optimistic that it can be further developed and applied.