Guanine nucleotide-binding proteins (G proteins) are involved as a modulator or transducer in various transmembrane signaling systems. This major G-protein of the squid photoreceptor is involved in visual transduction. The beta and gamma chains are required for the GTPase activity, for replacement of GDP by GTP, and for G protein-effector interaction (By similarity). Required for normal chemotaxis in response to cAMP. G proteins are composed of 3 units, alpha, beta and gamma. Interacts with gpbA, and this requires phlp1. Expressed in vegetative cells. Expression rises within 6 hours after the initiation of development and gradually decreases following the mound stage. This protein is thought to be subject to lipidation, and this requires phlp1. Belongs to the G protein gamma family.