Steroidogenic acute regulatory protein (StAR) facilitates the biosynthesis of steroid hormones by regulating the transfer of cholesterol from the outer to the inner mitochondrial membrane []. Mitochondrial fusion and ERK phosphorylation can direct StAR to the outer mitochondrial membrane to achieve a large number of steroid molecules per unit of StAR [, ].
This entry represents the homodimerisation domain of the STAR (signal transducer and activator of RNA) proteins. Quaking is a prototypical member of the STAR family, which plays key roles in post-transcriptional gene regulation by controlling mRNA translation, stability and splicing []. Quaking-dimer is a helix-turn-helix dimer with an additional helix in the turn region. The dimerisation of quaking is required for adequate RNA-binding [].
GLD-1 from Caenorhabditis nematodes belongs to the Signal Transduction and Activation of RNA (STAR)-domain family of RNA-binding proteins [, ], conserved throughout eukaryotes. All STAR proteins contain maxi K-homology (KH)-RNA binding domain. STAR proteins control a wide range of developmental events by regulating alternative splicing and translational repression of specific mRNA targets. GLD-1 functions in Caenorhabditis elegans as a germline-specific translational repressor [].This entry also includes protein held out wings (also known as how) from Drosophila melanogaster. How is a RNA-binding protein involved in the control of muscular and cardiac activity []. It also mediates cell adhesion processes [].
This family consists of cyclin-related protein FAM58A (also known as cyclin-Q or cyclin-M). Cyclin M is an orphan cyclin, whose mutations cause a human developmental anomaly known as STAR syndrome. It may be involved in regulation of ETS2, which plays key roles in cancer and development [].
This entry represents the guanylin family. Its members include guanylate cyclase activator 2A and 2B. They are endogenous activators of intestinal guanylate cyclases. Guanylin, a 15-amino-acid peptide, is an endogenous ligand of the intestinal receptor guanylate cyclase-C, known as STaR [, ]. Upon receptor binding, guanylin increases the intracellular concentration of cGMP, it induces chloride secretion and decreases intestinal fluid absorption, ultimately causing diarrhoea []. The peptide stimulates the enzyme through the same receptor binding region as the heat-stable enterotoxins [].
This entry includes EDR2 and EDR2L from Arabidopsis. They contain a pleckstrin homology and a StAR transfer (START) domain as well as a plant-specific domain of unknown function, DUF1336. EDR2 is a negative regulator of the salicylic acid- (SA-) mediated resistance to pathogens, including the biotrophic powdery mildew pathogens Golovinomyces cichoracearum and Blumeria graminis, and the downy mildew pathogen Hyaloperonospora parasitica, probably by limiting the initiation of cell death and the establishment of the hypersensitive response (HR) [, ].
This entry represents the guanylin superfamily. Its members include guanylate cyclase activator 2A and 2B. They are endogenous activators of intestinal guanylate cyclases. Guanylin, a 15-amino-acid peptide, is an endogenous ligand of the intestinal receptor guanylate cyclase-C, known as STaR [, ]. Upon receptor binding, guanylin increases the intracellular concentration of cGMP, it induces chloride secretion and decreases intestinal fluid absorption, ultimately causing diarrhoea []. The peptide stimulates the enzyme through the same receptor binding region as the heat-stable enterotoxins [].Guanylin structure has a beta(2)-alpha(3)-beta fold and two layers (alpha/beta) with an antiparallel sheet topology.
Proteins in this family contain the START domain. Their function is not clear.START (StAR-related lipid-transfer) is a lipid-binding domain in StAR, HD-ZIP and signalling proteins []. StAR (Steroidogenic Acute Regulatory protein) is a mitochondrial protein that is synthesised in response to luteinising hormone stimulation [].Expression of the protein in the absence of hormone stimulation is sufficient to inducesteroid production, suggesting that this protein is required in the acute regulation ofsteroidogenesis. Representatives of the START domain family havebeen shown to bind different ligands such as sterols (StAR protein) andphosphatidylcholine (PC-TP). Ligand binding by the START domain can alsoregulate the activities of other domains that co-occur with the START domainin multidomain proteins such as Rho-gap, the homeodomain,and the thioesterase domain [, ].
START (StAR-related lipid-transfer) is a lipid-binding domain in StAR, HD-ZIP and signalling proteins []. StAR (Steroidogenic Acute Regulatory protein) is a mitochondrial protein that is synthesised in response to luteinising hormone stimulation [].Expression of the protein in the absence of hormone stimulation is sufficient to inducesteroid production, suggesting that this protein is required in the acute regulation ofsteroidogenesis. Representatives of the START domain family havebeen shown to bind different ligands such as sterols (StAR protein) andphosphatidylcholine (PC-TP). Ligand binding by the START domain can alsoregulate the activities of other domains that co-occur with the START domainin multidomain proteins such as Rho-gap, the homeodomain,and the thioesterase domain [, ]. The crystal structure of START domain of human MLN64 shows analpha/beta fold built around an U-shaped incomplete β-barrel. Mostimportantly, the interior of the protein encompasses a 26 x 12 x 11 Angstromshydrophobic tunnel that is apparently large enough to bind a singlecholesterol molecule []. The START domain structure revealed an unexpectedsimilarity to that of the birch pollen allergen Bet v 1 and to bacterialpolyketide cyclases/aromatases [, ].
START (StAR-related lipid-transfer) is a lipid-binding domain in StAR, HD-ZIP and signalling proteins []. StAR (Steroidogenic Acute Regulatory protein) is a mitochondrial protein that is synthesised in response to luteinising hormone stimulation [].Expression of the protein in the absence of hormone stimulation is sufficient to inducesteroid production, suggesting that this protein is required in the acute regulation ofsteroidogenesis. Representatives of the START domain family havebeen shown to bind different ligands such as sterols (StAR protein) andphosphatidylcholine (PC-TP). Ligand binding by the START domain can alsoregulate the activities of other domains that co-occur with the START domainin multidomain proteins such as Rho-gap, the homeodomain,and the thioesterase domain [, ]. The crystal structure of START domain of human MLN64 shows analpha/beta fold built around an U-shaped incomplete β-barrel. Mostimportantly, the interior of the protein encompasses a 26 x 12 x 11 Angstromshydrophobic tunnel that is apparently large enough to bind a singlecholesterol molecule []. The START domain structure revealed an unexpectedsimilarity to that of the birch pollen allergen Bet v 1 and to bacterialpolyketide cyclases/aromatases [, ]. This superfamily represents an alpha/beta sandwich structural domain found in a wide variety of protein families, including STAR-related lipid transfer proteins and homeobox-leucine zipper proteins.
This entry represents the START-like domain distantly related to the START domain.START (StAR-related lipid-transfer) is a lipid-binding domain in StAR, HD-ZIP and signalling proteins []. StAR (Steroidogenic Acute Regulatory protein) is a mitochondrial protein that is synthesised in response to luteinising hormone stimulation [].Expression of the protein in the absence of hormone stimulation is sufficient to inducesteroid production, suggesting that this protein is required in the acute regulation ofsteroidogenesis. Representatives of the START domain family havebeen shown to bind different ligands such as sterols (StAR protein) andphosphatidylcholine (PC-TP). Ligand binding by the START domain can alsoregulate the activities of other domains that co-occur with the START domainin multidomain proteins such as Rho-gap, the homeodomain,and the thioesterase domain [, ]. The crystal structure of START domain of human MLN64 shows analpha/beta fold built around an U-shaped incomplete β-barrel. Mostimportantly, the interior of the protein encompasses a 26 x 12 x 11 Angstromshydrophobic tunnel that is apparently large enough to bind a singlecholesterol molecule []. The START domain structure revealed an unexpectedsimilarity to that of the birch pollen allergen Bet v 1 and to bacterialpolyketide cyclases/aromatases [, ].
