Translocons, thermodynamics, and the folding of membrane proteins.

Recent three-dimensional structures of helical membrane proteins present new challenges for the prediction of structure from amino acid sequence. Membrane proteins reside stably in a thermodynamic free energy minimum after release into the membrane's bilayer fabric from the translocon complex. This means that structure prediction is primarily a problem of physical chemistry. But the folding processes within the translocon must also be considered. A distilled overview of the physical principles of membrane protein stability is presented, and extended to encompass translocon-assisted folding.