This family consists of glycine rich proteins, including Arabidopsis AtGRP3 (At2g05520). AtGRP3 interacts with the receptor-like kinase AtWAK1 and functions in root size determination during development and in Aluminum stress [].
Gastrin-releasing peptide (GRP) is a mammalian neuropeptide, homologue of the amphibian bombesin. It binds to the GRP receptor (GRPR, also called BB2), a member of the G-protein coupled receptor (GPCR) superfamily []. It operates as a negative feedback regulating fear and established a causal relationship between GRP-receptor gene expression, long-term potentiation, and amygdala-dependent memory for fear [].
The region featured in this family is found repeated in a number of plant proteins, some of which are expressed specifically in nodules formed during symbiotic interactions with certain bacterial species]. Some of these proteins are also termed glycine-rich proteins (GRPs), due to the presence of a glycine-rich C-terminal region in their structures []. Bacterial infection is required for the induction of nodule-specific GRP genes, and it is thought that nodule-specific GRPs may play non-redundant roles required at specific stages of nodule development []. Members of this group of proteins may be cytosolic, whereas others are thought to be membrane-associated [].
This is the GASA gibberellin regulated cysteine rich protein (GRPs) family. The expression of these proteins is up-regulated by the plant hormone gibberellin, most of these proteins have a role in plant development and some of its members have antimicrobial activity [, ]. There are 12 cysteine residues conserved within the alignment giving the potential for these proteins to possess 6 disulphide bonds.Included in this family are some GRPs found in fruits and pollens that have been identified as allergens, including peach Pru p 7, Japanese apricot Pru m 7, orange Cit s 7, pomegranate Pun g 7, and cypress pollen GRP [, , ].
G protein-coupled receptors (GPCRs) constitute a vast protein family that encompasses a wide range of functions, including various autocrine, paracrine and endocrine processes. They show considerable diversity at the sequence level, on the basis of which they can be separated into distinct groups []. The term clan can be used to describe the GPCRs, as they embrace a group of families for which there are indications of evolutionary relationship, but between which there is no statistically significant similarity in sequence []. The currently known clan members include rhodopsin-like GPCRs (Class A, GPCRA), secretin-like GPCRs (Class B, GPCRB), metabotropic glutamate receptor family (Class C, GPCRC), fungal mating pheromone receptors (Class D, GPCRD), cAMP receptors (Class E, GPCRE) and frizzled/smoothened (Class F, GPCRF) [, , , , ]. GPCRs are major drug targets, and are consequently the subject of considerable research interest. It has been reported that the repertoire of GPCRs for endogenous ligands consists of approximately 400 receptors in humans and mice []. Most GPCRs are identified on the basis of their DNA sequences, rather than the ligand they bind, those that are unmatched to known natural ligands are designated by as orphan GPCRs, or unclassified GPCRs [].The rhodopsin-like GPCRs (GPCRA) represent a widespread protein family that includes hormone, neurotransmitter and light receptors, all of which transduce extracellular signals through interaction with guanine nucleotide-binding (G) proteins. Although their activating ligands vary widely in structure and character, the amino acid sequences of the receptors are very similar and are believed to adopt a common structural framework comprising 7 transmembrane (TM) helices [, , ].Bombesins are peptide neurotransmitters whose biological activity residesin a common C-terminal sequence, WAXGHXM. In the periphery, bombesin-related peptides stimulate smooth muscle and glandular secretion. In thebrain, these peptides are believed to play a role in homeostasis, thermoregulation and metabolism, and have been reported to elicit analgesia andexcessive grooming, together with central regulation of a variety ofperipheral effects.Mammalian bombesins are encoded by 2 genes. The preproGRP gene transcriptencodes a precursor of 147 amino acids, which gives GRP and GRP18-27. ThepreproNMB gene transcript encodes a precursor of 117 amino acids, which ismetabolised to neuromedin B. Receptors for these peptides have widespreaddistribution in peripheral tissue. High levels are found in smooth muscleand in the brain.The gastrin-releasing peptide receptor has a wide distribution in peripheraltissue. High levels are found in smooth muscle (e.g., intestine, stomachand bladder) and in secretory glands (e.g., pancreas). In the brain, it isfound in high levels in the hypothalamus, and is present in other areas inlower levels (e.g., the olfactory tract, dendate gyrus and cortex). Itis also found in various cell lines (e.g., Swiss 3T3 fibroblasts and small-cell lung carcinomas). GRP receptors activate the phosphoinositidepathway via a pertussis-toxin-insensitive G-protein, probably of the Gq/G11class.
G protein-coupled receptors (GPCRs) constitute a vast protein family that encompasses a wide range of functions, including various autocrine, paracrine and endocrine processes. They show considerable diversity at the sequence level, on the basis of which they can be separated into distinct groups []. The term clan can be used to describe the GPCRs, as they embrace a group of families for which there are indications of evolutionary relationship, but between which there is no statistically significant similarity in sequence []. The currently known clan members include rhodopsin-like GPCRs (Class A, GPCRA), secretin-like GPCRs (Class B, GPCRB), metabotropic glutamate receptor family (Class C, GPCRC), fungal mating pheromone receptors (Class D, GPCRD), cAMP receptors (Class E, GPCRE) and frizzled/smoothened (Class F, GPCRF) [, , , , ]. GPCRs are major drug targets, and are consequently the subject of considerable research interest. It has been reported that the repertoire of GPCRs for endogenous ligands consists of approximately 400 receptors in humans and mice []. Most GPCRs are identified on the basis of their DNA sequences, rather than the ligand they bind, those that are unmatched to known natural ligands are designated by as orphan GPCRs, or unclassified GPCRs [].The rhodopsin-like GPCRs (GPCRA) represent a widespread protein family that includes hormone, neurotransmitter and light receptors, all of which transduce extracellular signals through interaction with guanine nucleotide-binding (G) proteins. Although their activating ligands vary widely in structure and character, the amino acid sequences of the receptors are very similar and are believed to adopt a common structural framework comprising 7 transmembrane (TM) helices [, , ].Bombesins are peptide neurotransmitters whose biological activity residesin a common C-terminal sequence, WAXGHXM. In the periphery, bombesin-related peptides stimulate smooth muscle and glandular secretion. In thebrain, these peptides are believed to play a role in homeostasis, thermoregulation and metabolism, and have been reported to elicit analgesia andexcessive grooming, together with central regulation of a variety ofperipheral effects.Mammalian bombesins are encoded by 2 genes. The preproGRP gene transcriptencodes a precursor of 147 amino acids, which gives GRP and GRP18-27. ThepreproNMB gene transcript encodes a precursor of 117 amino acids, which ismetabolised to neuromedin B. Receptors for these peptides have widespreaddistribution in peripheral tissue. High levels are found in smooth muscleand in the brain.The neuromedin B receptor has been characterised in rat oesophagus and raturinary bladder. It is widespread in the CNS, and is found in highlevels in olfactory nucleus and thalamic regions, and in lower levels inthe frontal cortex, dendate gyrus, amygdala and dorsal raphe. Thereceptor activates the phosphoinositide pathway through a pertussis-toxin-insensitive G-protein, probably of the Gq/G11 class.
G protein-coupled receptors (GPCRs) constitute a vast protein family that encompasses a wide range of functions, including various autocrine, paracrine and endocrine processes. They show considerable diversity at the sequence level, on the basis of which they can be separated into distinct groups []. The term clan can be used to describe the GPCRs, as they embrace a group of families for which there are indications of evolutionary relationship, but between which there is no statistically significant similarity in sequence []. The currently known clan members include rhodopsin-like GPCRs (Class A, GPCRA), secretin-like GPCRs (Class B, GPCRB), metabotropic glutamate receptor family (Class C, GPCRC), fungal mating pheromone receptors (Class D, GPCRD), cAMP receptors (Class E, GPCRE) and frizzled/smoothened (Class F, GPCRF) [, , , , ]. GPCRs are major drug targets, and are consequently the subject of considerable research interest. It has been reported that the repertoire of GPCRs for endogenous ligands consists of approximately 400 receptors in humans and mice []. Most GPCRs are identified on the basis of their DNA sequences, rather than the ligand they bind, those that are unmatched to known natural ligands are designated by as orphan GPCRs, or unclassified GPCRs [].The rhodopsin-like GPCRs (GPCRA) represent a widespread protein family that includes hormone, neurotransmitter and light receptors, all of which transduce extracellular signals through interaction with guanine nucleotide-binding (G) proteins. Although their activating ligands vary widely in structure and character, the amino acid sequences of the receptors are very similar and are believed to adopt a common structural framework comprising 7 transmembrane (TM) helices [, , ].Bombesins are peptide neurotransmitters whose biological activity residesin a common C-terminal sequence, WAXGHXM. In the periphery, bombesin-related peptides stimulate smooth muscle and glandular secretion. In thebrain, these peptides are believed to play a role in homeostasis, thermo-regulation and metabolism, and have been reported to elicit analgesia andexcessive grooming, together with central regulation of a variety ofperipheral effects.Mammalian bombesins are encoded by 2 genes. The preproGRP gene transcriptencodes a precursor of 147 amino acids, which gives GRP and GRP18-27. ThepreproNMB gene transcript encodes a precursor of 117 amino acids, which ismetabolised to neuromedin B. Receptors for these peptides have widespreaddistribution in peripheral tissue. High levels are found in smooth muscleand in the brain.The recently-identified BRS-3 bombesin receptor subtype is found in germcells in testis and in uteri of pregnant animals; it is also present in avariety of lung carcinoma cell lines. The receptor is believed to playa role in sperm cell division and maturation. Its action is mediated byassociation with G-proteins that activate a phosphatidylinositol-calciumsecond messenger system.
