Guanine nucleotide-binding proteins (G proteins) function as transducers in numerous signaling pathways controlled by G protein-coupled receptors (GPCRs). Signaling involves the activation of adenylyl cyclases, resulting in increased levels of the signaling molecule cAMP. GNAS functions downstream of several GPCRs, including beta-adrenergic receptors. XLas isoforms interact with the same set of receptors as Gnas isoforms. G proteins are composed of 3 units; alpha, beta and gamma. The alpha chain contains the guanine nucleotide binding site. Interacts through its N-terminal region with ALEX which is produced from the same locus in a different open reading frame. This interaction may inhibit its adenylyl cyclase-stimulating activity (By similarity). Interacts with MAGED2. Mice cells lacking XLas isoforms which are then transfected with these isoforms and a range of receptors demonstrate that the XLas isoforms are capable of functionally coupling to the same receptors as the Gnas isoforms including Adrb2, Crfr1, Pthr1 and Tshr. This protein is produced by a bicistronic gene which also produces the ALEX protein from an overlapping reading frame. The GNAS locus is imprinted in a complex manner, giving rise to distinct paternally, maternally and biallelically expressed proteins. The XLas isoforms are paternally derived, the Gnas isoforms are biallelically derived and the Nesp55 isoforms are maternally derived. Belongs to the G-alpha family. G(s) subfamily.