Protein–protein interactions

We are proud to present the first edition of the Protein–protein interactions Section of Current Opinion in Structural Biology. The Section is new, but the topic has been present in the journal from the very start. Volume 1, Issue 1, dated February 1991, had a review by Janin entitled Protein–protein interactions and assembly, and others by Bode and Huber on Proteinase–inhibitor interaction, and by Chothia on Antigen recognition. The Editorial Overview, signed by TE Creighton and PS Kim, noted that ‘several new X-ray structures of protein complexes had been determined’, and stated that, for such complexes, the ‘overall goal was to understand the specificities of the binding reactions [and the] differential affinities’. At the time, most of the known structures displaying protein–protein interactions were oligomeric protein complexes, which are permanent assemblies. Protease–inhibi- tor and antigen–antibody complexes were the only examples of transient, although highly affine, interactions for which the questions of specificity and affinity could be raised, and therefore, the three reviews of Issue 1 pretty much covered the field. Soon afterwards, new X-ray structures illustrated the role of protein–protein interactions in several major cellular processes. A landmark was the structure of the transducin Ga–Gbg complex by Paul Sigler and collaborators (Lambright et al., 1996, Nature 379:311). Transducin is the G protein that is coupled with rhodopsin in the retina, a key step of the visual signal transduction. The Ga–Gbg complex has many features that had not been seen in earlier structures. It is short-lived, whereas protease–inhibitor and antigen–antibody complexes are stable for hours or days; it displays large conformation changes, all essential to function. The December 1997 issue of Current Opinion in Structural Biology reviewed that structure and those of other complexes involved in signal transduction. Many more were determined afterwards, and they have been reviewed on a regular basis in several Sections of the journal, first of all Folding and Binding, Catalysis and Regulation, and Macromolecular Assemblages.