377 GBB1_TOBAC Guanine nucleotide-binding proteins (G proteins) are involved as a modulator or transducer in various transmembrane signaling systems. The beta and gamma chains are required for the GTPase activity, for replacement of GDP by GTP, and for G protein- effector interaction. MSVTELKERHMAATQTVNDLREKLKQKRLQLLDTDVSGYARSQGKTPVTFGPTDLVCCRILQGHTGKVYSLDWTPEKNRIVSASQDGRLIVWNALTSQKTHAIKLPCAWVMTCAFSPSGQSVACGGLDSVCSIFNLNSPIDKDGNHPVSRMLSGHKGYVSSCQYVPDEDTHLITSSGDQTCVLWDITTGLRTSVFGGEFQSGHTADVQSVSISSSNPRLFVSGSCDTTARLWDTRVASRAQRTFYGHEGDVNTVKFFPDGNRFGTGSEDGTCRLFDIRTEHQLQVYYQPHGDGDIPHVTSMAFSISGRLLFVGYSNGDCYVWDTLLAKVVLNLGGVQNSHEGRISCLGLSADGSALCTGSWDTNLKIWAFGGHRSVI Guanine nucleotide-binding protein subunit beta-1