Component of a heterodimeric G-protein coupled receptor for GABA, formed by GABBR1 and GABBR2 (PubMed:10773016, PubMed:10075644). Within the heterodimeric GABA receptor, only GABBR1 seems to bind agonists, while GABBR2 mediates coupling to G proteins (By similarity). Ligand binding causes a conformation change that triggers signaling via guanine nucleotide-binding proteins (G proteins) and modulates the activity of down-stream effectors, such as adenylate cyclase (PubMed:10773016, PubMed:10075644). Signaling inhibits adenylate cyclase, stimulates phospholipase A2, activates potassium channels, inactivates voltage-dependent calcium-channels and modulates inositol phospholipid hydrolysis (PubMed:10075644). Calcium is required for high affinity binding to GABA (By similarity). Plays a critical role in the fine-tuning of inhibitory synaptic transmission (By similarity). Pre-synaptic GABA receptor inhibits neurotransmitter release by down-regulating high-voltage activated calcium channels, whereas postsynaptic GABA receptor decreases neuronal excitability by activating a prominent inwardly rectifying potassium (Kir) conductance that underlies the late inhibitory postsynaptic potentials (PubMed:10075644). Not only implicated in synaptic inhibition but also in hippocampal long-term potentiation, slow wave sleep, muscle relaxation and antinociception (By similarity). Heterodimer of GABBR1 and GABBR2 (PubMed:10773016, PubMed:10075644, PubMed:9872744). Homodimers may form, but are inactive (By similarity). Interacts (via C-terminus) with ATF4 (via leucine zipper domain) (By similarity). Interacts with JAKMIP1 (PubMed:14718537). Coexpression of GABBR1 and GABBR2 is required for GABBR1 maturation and transport to the plasma membrane. Colocalizes with ATF4 in hippocampal neuron dendritic membranes (By similarity). Expressed in neuronal tissue including cortex, cerebellum and spinal cord. Not detected in non-neuronal tissues including heart, liver, spleen and kidney. Alpha-helical parts of the C-terminal intracellular region mediate heterodimeric interaction with GABBR2. The linker region between the transmembrane domain 3 (TM3) and the transmembrane domain 4 (TM4) probably plays a role in the specificity for G-protein coupling. Belongs to the G-protein coupled receptor 3 family. GABA-B receptor subfamily.