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Created page with "== Introduction == Guanine nucleotide-binding proteins (G proteins) are a family of proteins involved in transmitting chemical signals outside the cell, and causing changes inside the cell. They communicate signals from a variety of stimuli outside a cell to its interior. G proteins are so called because they bind the guanine nucleotides GDP and GTP. Image:Detail-59220.jpg|thumb|center|A close-up view of a G protein..."