Folding and stability of membrane transport proteins in vitro

Transmembrane transporters are responsible for maintaining a correct internal cellular environment. The inherent flexibility of transporters together with their hydrophobic environment means that they are challenging to study in vitro, but recently significant progress been made. This review will focus on in vitro stability and folding studies of transmembrane alpha helical transporters, including reversible folding systems and thermal denaturation. The successful re-assembly of a small number of ATP binding cassette transporters is also described as this is a significant step forward in terms of understanding the folding and assembly of these more complex, multi-subunit proteins. The studies on transporters discussed here represent substantial advances for membrane protein studies as well as for research into protein folding. The work demonstrates that large flexible hydrophobic proteins are within reach of in vitro folding studies, thus holding promise for furthering knowledge on the structure, function and biogenesis of ubiquitous membrane transporter families. This article is part of a Special Issue entitled: Protein Folding in Membranes.