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        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 157502958   1 RYIDWLITVPLQMVEFYLILSAVGKANSGMFWRLLLGSVVMLVGGYLGEAG--YINATLGFIIGMAGWVYILYEVFSGEA 78
Cdd:cd15242   79 RYVDWLLTVPLLLIEFYLVLALAGAETSSLLWRLGGASALMIVLGYPGEIGadLGTRWLWGVLSMIPFLYIIYELFVGLA 158

                         90       100       110       120
                 ....*....|....*....|....*....|....*....|..
gi 157502958  79 GKAAAKSGNKAlvTAFGAMRMIVTVGWAIYPLGYVFGYLTGG 120
Cdd:cd15242  159 KAIARQPAAVR--GAVNTLRWIVLVGWAIYPIGYMAGYLGLT 198

green- and blue-light absorbing proteorhodopsins, member of the seven-transmembrane GPCR superfamily; This subgroup represents blue-light absorbing and green-light absorbing proteorhodopsins (PRs), which act as a light-driven proton pump that plays a major role in supplying light energy for phototropic marine microorganisms, by a mechanism similar to that of bacteriorhodopsin. PRs are found in most marine bacteria in surface waters, as well as in archaea and eukaryotes. They belong to the microbial rhodopsin family, also known as type 1 rhodopsins, comprising the light-driven inward chloride pump halorhodopsin (HR), the light-gated cation channel channelrhodopsin (ChR), the light-sensor activating transmembrane transducer protein sensory rhodopsin II (SRII), the light-sensor activating soluble transducer protein Anabaena sensory rhodopsin (ASR), and the other light-driven proton pumps such as bacteriorhodopsin (BR). They have been found in various single-celled microorganisms from all three domains of life, including halophile archaea, gamma-proteobacteria, cyanobacteria, fungi, and green algae. While microbial (type 1) and animal (type 2) rhodopsins have no sequence similarity with each other, they share a common architecture consisting of seven-transmembrane alpha-helices (TM) connected by extracellular loops and intracellular loops. Both types of rhodopsins consist of opsin and a covalently attached retinal (the aldehyde of vitamin A), a photoreactive chromophore, via a protonated Schiff base linkage to an amino group of lysine in the middle of the seventh transmembrane helix (TM7). Upon the absorption of light, microbial rhodopsins undergo light-induced photoisomerization of all-trans retinal into the 13-cis isomer, whereas the photoisomerization of 11-cis retinal to all-trans isomer occurs in the animal rhodopsins. While animal visual rhodopsins are activated by light to catalyze GDP/GTP exchange in the alpha subunit of the retinal G protein transducin (Gt), microbial rhodopsins do not activate G proteins, but instead can function as light-dependent ion pumps, cation channels, and sensors.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 157502958   1 RYIDWLITVPLQMVEFYLILSAVGKANSGMFWRLLLGSVVMLVGGYLGEAG--YINATLGFIIGMAGWVYILYEVFSGEA 78
Cdd:cd15242   79 RYVDWLLTVPLLLIEFYLVLALAGAETSSLLWRLGGASALMIVLGYPGEIGadLGTRWLWGVLSMIPFLYIIYELFVGLA 158

                         90       100       110       120
                 ....*....|....*....|....*....|....*....|..
gi 157502958  79 GKAAAKSGNKAlvTAFGAMRMIVTVGWAIYPLGYVFGYLTGG 120
Cdd:cd15242  159 KAIARQPAAVR--GAVNTLRWIVLVGWAIYPIGYMAGYLGLT 198

Bacteriorhodopsin [Energy production and conversion, Signal transduction mechanisms];

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 157502958   1 RYIDWLITVPLQMVEFYLILsavgKANSGMFWRLLLGSVVMLVGGYLGEAGYINA-TLGFIIGMAGWVYILYEVFSGEAG 79
Cdd:COG5524   71 RYIDWLLTTPLLLLELGLLA----GASRRLLVTLVGADVLMIVTGLAGALSTGPArWLWGLLSTAAFLVILYLLLGPLRR 146

                         90       100       110
                 ....*....|....*....|....*....|....*.
gi 157502958  80 KAAAKSGnkALVTAFGAMRMIVTVGWAIYPLGYVFG 115
Cdd:COG5524  147 SAARQGG--EVRSLFGKLRNLLVVLWLIYPIVWLLG 180

green- and blue-light absorbing proteorhodopsins, member of the seven-transmembrane GPCR superfamily; This subgroup represents blue-light absorbing and green-light absorbing proteorhodopsins (PRs), which act as a light-driven proton pump that plays a major role in supplying light energy for phototropic marine microorganisms, by a mechanism similar to that of bacteriorhodopsin. PRs are found in most marine bacteria in surface waters, as well as in archaea and eukaryotes. They belong to the microbial rhodopsin family, also known as type 1 rhodopsins, comprising the light-driven inward chloride pump halorhodopsin (HR), the light-gated cation channel channelrhodopsin (ChR), the light-sensor activating transmembrane transducer protein sensory rhodopsin II (SRII), the light-sensor activating soluble transducer protein Anabaena sensory rhodopsin (ASR), and the other light-driven proton pumps such as bacteriorhodopsin (BR). They have been found in various single-celled microorganisms from all three domains of life, including halophile archaea, gamma-proteobacteria, cyanobacteria, fungi, and green algae. While microbial (type 1) and animal (type 2) rhodopsins have no sequence similarity with each other, they share a common architecture consisting of seven-transmembrane alpha-helices (TM) connected by extracellular loops and intracellular loops. Both types of rhodopsins consist of opsin and a covalently attached retinal (the aldehyde of vitamin A), a photoreactive chromophore, via a protonated Schiff base linkage to an amino group of lysine in the middle of the seventh transmembrane helix (TM7). Upon the absorption of light, microbial rhodopsins undergo light-induced photoisomerization of all-trans retinal into the 13-cis isomer, whereas the photoisomerization of 11-cis retinal to all-trans isomer occurs in the animal rhodopsins. While animal visual rhodopsins are activated by light to catalyze GDP/GTP exchange in the alpha subunit of the retinal G protein transducin (Gt), microbial rhodopsins do not activate G proteins, but instead can function as light-dependent ion pumps, cation channels, and sensors.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 157502958   1 RYIDWLITVPLQMVEFYLILSAVGKANSGMFWRLLLGSVVMLVGGYLGEAG--YINATLGFIIGMAGWVYILYEVFSGEA 78
Cdd:cd15242   79 RYVDWLLTVPLLLIEFYLVLALAGAETSSLLWRLGGASALMIVLGYPGEIGadLGTRWLWGVLSMIPFLYIIYELFVGLA 158

                         90       100       110       120
                 ....*....|....*....|....*....|....*....|..
gi 157502958  79 GKAAAKSGNKAlvTAFGAMRMIVTVGWAIYPLGYVFGYLTGG 120
Cdd:cd15242  159 KAIARQPAAVR--GAVNTLRWIVLVGWAIYPIGYMAGYLGLT 198

Bacteriorhodopsin [Energy production and conversion, Signal transduction mechanisms];

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 157502958   1 RYIDWLITVPLQMVEFYLILsavgKANSGMFWRLLLGSVVMLVGGYLGEAGYINA-TLGFIIGMAGWVYILYEVFSGEAG 79
Cdd:COG5524   71 RYIDWLLTTPLLLLELGLLA----GASRRLLVTLVGADVLMIVTGLAGALSTGPArWLWGLLSTAAFLVILYLLLGPLRR 146

                         90       100       110
                 ....*....|....*....|....*....|....*.
gi 157502958  80 KAAAKSGnkALVTAFGAMRMIVTVGWAIYPLGYVFG 115
Cdd:COG5524  147 SAARQGG--EVRSLFGKLRNLLVVLWLIYPIVWLLG 180

type 1 opsins, member of the seven-transmembrane GPCR superfamily; This group represents the microbial rhodopsin family, also known as type 1 rhodopsins, which can function as light-dependent ion pumps, cation channels, and sensors. They have been found in various single-celled microorganisms from all three domains of life, including halophile archaea, gamma-proteobacteria, cyanobacteria, fungi, and green algae. Members of the type I rhodopsin family include: light-driven inward chloride pump halorhodopsin (HR); light-driven outward proton pump bacteriorhodopsin (BR); light-gated cation channel channelrhodopsin (ChR); light-sensor activating transmembrane transducer proteins, sensory rhodopsin I and II (SRI and II); light-sensor activating soluble transducer protein Anabaena sensory rhodopsin (ASR); and other light-driven proton pumps such as blue-light-absorbing and green-light absorbing proteorhodopsins, among others. While microbial (type 1) and animal (type 2) rhodopsins have no sequence similarity with each other, they share a common architecture consisting of seven-transmembrane alpha-helices (TM) connected by extracellular loops and intracellular loops. Both types of rhodopsins consist of opsin and a covalently attached retinal (the aldehyde of vitamin A), a photoreactive chromophore, via a protonated Schiff base linkage to an amino group of lysine in the middle of the seventh transmembrane helix (TM7). Upon the absorption of light, microbial rhodopsins undergo light-induced photoisomerization of all-trans retinal into the 13-cis isomer, whereas the photoisomerization of 11-cis retinal to all-trans isomer occurs in the animal rhodopsins. While animal visual rhodopsins are activated by light to catalyze GDP/GTP exchange in the alpha subunit of the retinal G protein transducin (Gt), microbial rhodopsins do not activate G proteins.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 157502958   1 RYIDWLITVPLQMVEfyliLSAVGKANSGMFWRLLLGSVVMLVGGYLGEAGYINAT--LGFIIGMAGWVYILYEVFSGEA 78
Cdd:cd14965   70 RYIDWLLTTPLILLD----LGLLAGADRATILALIGADVIMIVTGLIGALSIVTTVkwLWFLIGLCAFIVVLYGLAKNYR 145

                         90       100       110
                 ....*....|....*....|....*....|....*...
gi 157502958  79 GKAAAKSGNKAlvTAFGAMRMIVTVGWAIYPLGYVFGY 116
Cdd:cd14965  146 EAAKAKSPEVA--SLYTKLAWLTIVLWIAYPIVWIFGE 181

viral group II rhodopsins such as OLPVRII and similar proteins, members of the seven-transmembrane GPCR superfamily; The viral group II rhodopsins includes Organic Lake Phycodnavirus rhodopsin II (OLPVRII), a pentameric light-gated channel that is functionally analogous to well-studied pentameric ligand-gated ion channels playing crucial roles in many cellular processes. It is most likely specific for chloride. Members of this group are considered homologs of proteorhodopsins (PRs), which are blue-light absorbing and green-light absorbing proteins acting as light-driven proton pumps that play a major role in supplying light energy for phototropic marine microorganisms, by a mechanism similar to that of bacteriorhodopsin. Viral proteorhodopsins are predicted to function as sensory rhodopsins that could affect signaling, for example, phototaxis in the infected protists, perhaps stimulating relocation of the infected protists to areas that are rich in nutrients required for virus reproduction. PRs belong to the microbial rhodopsin family, also known as type 1 rhodopsins, which also comprise the light-driven inward chloride pump halorhodopsin (HR), the light-gated cation channel channelrhodopsin (ChR), the light-sensor activating transmembrane transducer protein sensory rhodopsin II (SRII), the light-sensor activating soluble transducer protein Anabaena sensory rhodopsin (ASR), and the other light-driven proton pumps such as bacteriorhodopsin (BR). While microbial (type 1) and animal (type 2) rhodopsins have no sequence similarity with each other, they share a common architecture consisting of seven-transmembrane alpha-helices (TM) connected by extracellular loops and intracellular loops. Both types of rhodopsins consist of opsin and a covalently attached retinal (the aldehyde of vitamin A), a photoreactive chromophore, via a protonated Schiff base linkage to an amino group of lysine in the middle of the seventh transmembrane helix (TM7). Upon the absorption of light, microbial rhodopsins undergo light-induced photoisomerization of all-trans retinal into the 13-cis isomer, whereas the photoisomerization of 11-cis retinal to all-trans isomer occurs in the animal rhodopsins. While animal visual rhodopsins are activated by light to catalyze GDP/GTP exchange in the alpha subunit of the retinal G protein transducin (Gt), microbial rhodopsins do not activate G proteins, but instead can function as light-dependent ion pumps, cation channels, and sensors.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 157502958   1 RYIDWLITVPLQMVEFYLILSAVGKANSGMFWRLLLGSVV---MLVGGYLGEAGYINAT------LGFIIGMAGWVYILY 71
Cdd:cd21087   69 RYVDWMITTPIMLLVLVLAFRYNTNKAMVKFSDFLIVLVLnygMLGTGYLGEIGVIHKTmaniigFGFFGGLFYYLYTKF 148

viral rhodopsins and similar proteins, members of the seven-transmembrane GPCR superfamily; This subfamily is composed of viral homologs of proteorhodopsins (PRs), which are blue-light absorbing and green-light absorbing proteins acting as light-driven proton pumps that play a major role in supplying light energy for phototropic marine microorganisms, by a mechanism similar to that of bacteriorhodopsin. Viral proteorhodopsins are predicted to function as sensory rhodopsins that could affect signaling, for example, phototaxis in the infected protists, perhaps stimulating relocation of the infected protists to areas that are rich in nutrients required for virus reproduction. Viral proteorhodopsins are monophyletic and split into two distinct groups, I and II, represented by Phaeocystis globosa virus 12T VirRDTS and Organic Lake phycodnavirus OLPVRII, respectively. PRs belong to the microbial rhodopsin family, also known as type 1 rhodopsins, which also comprise the light-driven inward chloride pump halorhodopsin (HR), the light-gated cation channel channelrhodopsin (ChR), the light-sensor activating transmembrane transducer protein sensory rhodopsin II (SRII), the light-sensor activating soluble transducer protein Anabaena sensory rhodopsin (ASR), and the other light-driven proton pumps such as bacteriorhodopsin (BR). While microbial (type 1) and animal (type 2) rhodopsins have no sequence similarity with each other, they share a common architecture consisting of seven-transmembrane alpha-helices (TM) connected by extracellular loops and intracellular loops. Both types of rhodopsins consist of opsin and a covalently attached retinal (the aldehyde of vitamin A), a photoreactive chromophore, via a protonated Schiff base linkage to an amino group of lysine in the middle of the seventh transmembrane helix (TM7). Upon the absorption of light, microbial rhodopsins undergo light-induced photoisomerization of all-trans retinal into the 13-cis isomer, whereas the photoisomerization of 11-cis retinal to all-trans isomer occurs in the animal rhodopsins. While animal visual rhodopsins are activated by light to catalyze GDP/GTP exchange in the alpha subunit of the retinal G protein transducin (Gt), microbial rhodopsins do not activate G proteins, but instead can function as light-dependent ion pumps, cation channels, and sensors.

                         10        20        30        40        50        60        70
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|.
gi 157502958   1 RYIDWLITVPLQMVEFYL---------ILSAVGKANSGMFWRLLLGSVVMLVGGYLGEAGYINATLGFIIG 62
Cdd:cd21061   70 RYVDWYITTPIMLLVLVLafeynnsddIISVFLKQKFSDFFYILFLNYGMLGFGYLGEINVIPKLLSNIIG 140