Dynamics of protein complex components

Identifying protein-protein interactions (PPIs) is necessary to understand the molecular mechanisms behind cellular processes. This task is complicated by the facts that many proteins can interact simultaneously (i.e. a protein complex) and may participate in more than one distinct complex. Because of this, a large number of combinatorial arrangements are possible, both of PPIs and complexes, making it a difficult task to identify all truly interacting proteins. Protein interactions also range from stable to highly transient assemblies, with lifetimes on the order of seconds [ 1 ]. Therefore, studies identifying PPIs must not only contend with the arrangement of proteins into PPIs and complexes, but the stability of the interactions as well. Because of the difficulty of the task, many approaches have been used to identify and study the dynamics of PPIs. In this review, we will summarize a number of the techniques currently used to identify protein-protein interactions, with a focus on recent developments.