seven-transmembrane G protein-coupled receptor superfamily; This hierarchical evolutionary model represents the seven-transmembrane (7TM) receptors, often referred to as G protein-coupled receptors (GPCRs), which transmit physiological signals from the outside of the cell to the inside via G proteins. GPCRs constitute the largest known superfamily of transmembrane receptors across the three kingdoms of life that respond to a wide variety of extracellular stimuli including peptides, lipids, neurotransmitters, amino acids, hormones, and sensory stimuli such as light, smell and taste. All GPCRs share a common structural architecture comprising of seven-transmembrane (TM) alpha-helices interconnected by three extracellular and three intracellular loops. A general feature of GPCR signaling is agonist-induced conformational changes in the receptors, leading to activation of the heterotrimeric G proteins, which consist of the guanine nucleotide-binding G-alpha subunit and the dimeric G-beta-gamma subunits. The activated G proteins then bind to and activate numerous downstream effector proteins, which generate second messengers that mediate a broad range of cellular and physiological processes. However, some 7TM receptors, such as the type 1 microbial rhodopsins, do not activate G proteins. Based on sequence similarity, GPCRs can be divided into six major classes: class A (the rhodopsin-like family), class B (the Methuselah-like, adhesion and secretin-like receptor family), class C (the metabotropic glutamate receptor family), class D (the fungal mating pheromone receptors), class E (the cAMP receptor family), and class F (the frizzled/smoothened receptor family). Nearly 800 human GPCR genes have been identified and are involved essentially in all major physiological processes. Approximately 40% of clinically marketed drugs mediate their effects through modulation of GPCR function for the treatment of a variety of human diseases including bacterial infections.

                        10
                ....*....|....*
gi 29611447  18 IIQRVFVWVVSAITC 32
Cdd:cd15965   1 IVQRVFVWVVSAVTC 15

relaxin receptor 1 (or LGR7), member of the class A family of seven-transmembrane G protein-coupled receptors; Relaxin is a member of the insulin superfamily that has diverse actions in both reproductive and non-reproductive tissues. The relaxin-like peptide family includes relaxin-1, relaxin-2, and the insulin-like (INSL) peptides such as INSL3, INSL4, INSL5 and INSL6. The relaxin family peptides share high structural but low sequence similarity, and exert their physiological functions by activating a group of four G protein-coupled receptors, RXFP1-4. Relaxin is the endogenous ligand for RXFP1, which has a large extracellular N-terminal domain containing 10 leucine-rich repeats and a unique low-density lipoprotein type A (LDLa) module which is necessary for receptor activation. Upon receptor binding, relaxin activates a variety of signaling pathways to produce second messengers such as cAMP and nitric oxide. RXFP1 is expressed in various tissues including uterus, ovary, placenta, cerebral cortex, heart, lung and kidney, among others.

                        10
                ....*....|....*
gi 29611447  18 IIQRVFVWVVSAITC 32
Cdd:cd15965   1 IVQRVFVWVVSAVTC 15

relaxin receptor 1 (or LGR7), member of the class A family of seven-transmembrane G protein-coupled receptors; Relaxin is a member of the insulin superfamily that has diverse actions in both reproductive and non-reproductive tissues. The relaxin-like peptide family includes relaxin-1, relaxin-2, and the insulin-like (INSL) peptides such as INSL3, INSL4, INSL5 and INSL6. The relaxin family peptides share high structural but low sequence similarity, and exert their physiological functions by activating a group of four G protein-coupled receptors, RXFP1-4. Relaxin is the endogenous ligand for RXFP1, which has a large extracellular N-terminal domain containing 10 leucine-rich repeats and a unique low-density lipoprotein type A (LDLa) module which is necessary for receptor activation. Upon receptor binding, relaxin activates a variety of signaling pathways to produce second messengers such as cAMP and nitric oxide. RXFP1 is expressed in various tissues including uterus, ovary, placenta, cerebral cortex, heart, lung and kidney, among others.

                        10
                ....*....|....*
gi 29611447  18 IIQRVFVWVVSAITC 32
Cdd:cd15965   1 IVQRVFVWVVSAVTC 15