Computational searching and mutagenesis suggest a structure for the pentameric transmembrane domain of phospholamban

Structural and environmental constraints greatly simplify the folding problem for membrane proteins. Computational methods can be used in a global search to find a small number of chemically reasonable models within these constraints, such that a modest set of experimental data can distinguish among them. We show that, for phospholamban, the global search can be further simplified by reducing the problem to two-body, rather than many-body, interactions. This method of a constrained global search combined with experimental mutagenesis data yields a three-dimensional structure for this pentameric ion channel. The model is a left-handed symmetric homopentamer of a-helices with a well-defined channel, lined solely by hydrophobic residues.