HOW TO HUNT FOR INTERACTION PARTNERS OF MEMBRANE PROTEINS IN VIVO?

Abstract

Membrane proteins consist approximately 30% of the genes of an average organism and they are critical for several cell functions, such as signaling, energy transduction and division. Moreover, large amount of soluble proteins are known to be associated with membrane proteins. As much as function of single proteins, protein interaction networks play a crucial role in homeostasis. Up to date, affinity-based methods, such as pull-down or co-immunoprecipitation, were employed to identify many protein-protein interactions. However, a set of these methods cannot be applied to membrane proteins readily. Moreover, these approaches may fail in the presence of weak or transient interactions. Here, we present two techniques, advanced yeast two-hybrid systems and incorporation of in vivo photo-cross-linking unnatural amino acids, to study membrane protein-protein interactions in vivo. These two techniques are also applicable, with the help of improved cDNA expression libraries, to fish unidentified interactions on membranes.