Guanine nucleotide-binding proteins (G proteins) are involved as modulators or transducers in various transmembrane signaling systems. The G(i) proteins are involved in hormonal regulation of adenylate cyclase: they inhibit the cyclase in response to beta-adrenergic stimuli. May play a role in cell division. G proteins are composed of 3 units; alpha, beta and gamma. The alpha chain contains the guanine nucleotide binding site. In this context, interacts with GNB2 (By similarity). Interacts with UNC5B (By similarity). Interacts with GPSM1 (PubMed:11121039). Interacts with RGS12 and RGS14 (PubMed:11387333). Interacts (inactive GDP-bound form) with NUCB1 (via GBA motif); the interaction leads to activation of GNAI3 (PubMed:21653697). Interacts (inactive GDP-bound form) with CCDC88C/DAPLE (via GBA motif) (By similarity). Interacts (inactive GDP-bound form) with CCDC8A/GIV (via GBA motif) (PubMed:19211784). Localizes in the centrosomes of interphase and mitotic cells. Detected at the cleavage furrow and/or the midbody (By similarity). Belongs to the G-alpha family. G(i/o/t/z) subfamily.