Co-immunoprecipitation. Identification of interacting proteins.

Abstract

The targeting of proteins, via precise protein-protein interactions, to specific intracellular locations, is a recurring theme in cell biology. This has become particularly evident from the explosion of recent studies in the general area of signal transduction. Over the past 5–10 yr great strides have been made in understanding the intracellular signaling processes that regulate proliferative, metabolic, and other cellular responses. These mechanisms are complex and usually involve the participation of many signaling molecules linked by a series of catalytic and noncatalytic interactions. The physical association of two or more proteins in a signaling pathway is necessary in order to attain efficiency of signaling and to maintain specificity of response. A number of categories of protein-protein interaction are known to occur. These include the interaction between enzyme and substrate, the interaction between src homology 2 (SH2) domains and phosphotyrosyl residues within specific peptide sequences, and the binding of SH3 domains to polyprolyl sequences (). The development of techniques that can provide evidence for the interaction of two or more proteins in the intact cell has been instrumental in establishing the existence of many signaling pathways. This chapter aims to describe one such technique, that of co-immunoprecipitation.