Santa Cruz Biotechnology offers an expansive library of transfected lysates that overexpress GTP/GDP binding proteins. Guanosine triphosphate (GTP)/guanosine diphosphate (GDP)-binding proteins have a different conformation depending on whether they are bound to GTP or GDP. GTP usually stabilizes the active conformation of these proteins, and hydrolysis of the bound GTP to GDP + Pi usually causes the protein to become inactive. Reactivation occurs when the bound GDP is released in exchange for GTP. Heterotrimeric G-proteins, short for guanine nucleotide binding proteins, are a family of GTP-binding proteins that play a role in second messenger cascades. Members of the family of small GTP-binding proteins have a broad range of functions, most of which pertain to cell communication and signaling cascades. Examples of such important GTP/GDP binding proteins include Rac, Rho, Ras, Vav and C3G. Transfected lysates that express GTP/GDP binding proteins offer a reliable means to evaluate antibody quality and serve as excellent positive controls for experiments involving antibodies.