Trimeric G Proteins—Surprise Witness Tells a Tale

This is the authors' abstract. We don't add key points for this paper.

H. Bourne comments on an unusual polymeric crystal structure for the alpha subunit of the heterotrimeric G protein presented in this issue of Science by Mixon et al . ( p. 954 ). Although he questions the authors' suggestion that G alpha might exist as a polymer in the cell, he shows how a domain consisting of the amino and carboxyl terminal ends of the protein, evident in the polymeric structure, may be revealing how G alpha catalyzes GTP-GDP exchange.