Conformational transition of a membrane-bound model protein

An integral protein is a collapsed macromolecule whose conformation is determined uniquely by its amino acid sequence, but there appear common conformational features observed in vivo. Inside the membrane, proteins usually form alpha-helical domains, while random excursions of the protein strands appear outside the membrane. In this study, protein molecules are assumed to be a hydrophobic homopolymer capable of forming hydrogen bonds with other segments, which enables it to build up alpha-helical structures. Statistical weight for each subunit of an integral protein is quantified and most probable conformational status is determined via the grand canonical ensemble approach. As the temperature varies, protein conformation changes drastically near transition points, where the effect of membrane hydrophobicity is found to be important in determining the integral protein integration pathway.