Guanine nucleotide-binding proteins (G proteins) are involved as modulators or transducers in various transmembrane signaling systems (PubMed:10192394). This specific G-alpha subunit plays an important role in olfaction and in cilia morphogenesis (PubMed:9459442, PubMed:15342507). Involved in chemotactic responses to attractants diacetyl, pyrazine, 2,4,5-trimethylthiazole, benzaldehyde, isoamyl alcohol, butanone and 2,3-pentanedione (PubMed:12694294). Displays a redundant function with gpa-3 in chemotactic responses (PubMed:12694294). Plays a role in the avoidance response to the noxious chemical quinine in ASH sensory neurons (PubMed:14988722). Involved in avoidance responses to copper, sodium dodecyl sulfate and linoleic acid (PubMed:12694294). Involved in osmotic avoidance and mechanosensory responses (PubMed:12694294). Involved in specifying fan-like morphology of cilia of head sensory neurons AWC (PubMed:9459442). Plays a role in the detection of preferred food sources by mediating the recognition of food odors in olfactory sensory neurons (PubMed:25009271). G proteins are composed of 3 units; alpha, beta and gamma. The alpha chain contains the guanine nucleotide binding site (By similarity). In amphid neurons also weakly expressed in cell body. In phasmid neurons found only in cilia. Expressed in sensory neurons in the head and tail. Expressed in amphid AWC neurons, to a lesser extent in AWB and weakly in AWA, ASH and ADF neurons (head sensory neurons). Expressed in phasmid PHA and PHB neurons (tail sensory neurons). Defective in chemotactic responses to attractants and repellents and in osmotic and mechanosensory avoidance. Belongs to the G-alpha family.