This entry represents the Ninja family of proteins, which play a role in stress-related and growth-related signalling cascades []. In Arabidopsis thaliana, Ninja (also known as AFP homologue 2, At4g28910) is a negative regulator of jasmonate responses. Through protein Ninja, Jasmonate ZIM-domain (JAZ) repressor proteins recruit the Groucho/Tup1-type co-repressor TOPLESS (TPL) and TPL-related proteins (TPRs) []. Ninja-family proteins AFP1 and AFP4 have been shown to act as negative regulators of the abscisic acid (ABA) response [].
Antifreeze proteins (AFPs) are a class of proteins that are able to bind to and inhibit the growth of macromolecular ice, thereby permitting an organism to survive subzero temperatures by decreasing the probability of ice nucleation in their bodies []. These proteins have been characterised from a variety of organisms, including fish, plants, bacteria, fungi and arthropods. This entry represents insect AFPs of the type found in Tenebrio molitor iridescent virus and in Dendroides canadensis (Pyrochroid beetle).The structure of these AFPs consists of a right-handed β-helix with 12 residues per coil. The β-helices of insect AFPs present a highly rigid array of threonine residues and bound water molecules that can effectively mimic the ice lattice. As such, β-helical AFPs provide a more effective coverage of the ice surface compared to the α-helical fish AFPs [].A second insect antifreeze from Choristoneura fumiferana (Spruce budworm) () also consists of β-helices, however in these proteins the helices form a left-handed twist; these proteins show no sequence homology to the current entry, but may act by a similar mechanism. The β-helix motif may be used as an AFP structural motif in non-homologous proteins from other (non-fish) organisms as well.
Antifreeze proteins (AFPs) are defined by their ability to bind ice and prevent it from growing. In this way they function inboth freeze-resistance and freeze-tolerance strategies of organisms that live at sub-zero temperatures and require protection from ice growth. In fish, five AFP types have been described that are remarkably diverse in their 3D structures. They have completely dissimilar folds and no sequence homology. Type III AFPs found in eelpouts are 65-residue proteins with a compact globular fold formed from short β-strands, which presents a flat ice binding surface. These proteins are homologous to the C-terminal region of mammalian and prokaryotic sialic acid synthase (SAS; gene neuB), which has been called AFP-like domain []. The similarity is greatest in the protein core and the flat ice-binding region. SAS is involved in the condensation of phosphoenolpyruvate with N-acetylmannosamine derivatives to generate N-acetylneuraminic acid, an intermediate used for the sialylation of glycoconjugates. The function of the AFP-like domain, which is a β-clip fold [], in SAS is not known, but it has been proposed that it could be involved in sugar binding.
Antifreeze proteins (AFPs) are a class of proteins that are able to bind to and inhibit the growth of macromolecular ice, thereby permitting an organism to survive subzero temperatures by decreasing the probability of ice nucleation in their bodies []. These proteins have been characterised from a variety of organisms, including fish, plants, bacteria, fungi and arthropods. This entry represents insect AFPs of the type found in spruce budworm, Choristoneura fumiferana.The structure of these AFPs consists of a left-handed β-helix with 15 residues per coil []. The β-helices of insect AFPs present a highly rigid array of threonine residues and bound water molecules that can effectively mimic the ice lattice. As such, β-helical AFPs provide a more effective coverage of the ice surface compared to the α-helical fish AFPs.A second insect antifreeze from Tenebrio molitor () also consists of β-helices, however in these proteins the helices form a right-handed twist; these proteins show no sequence homology to the current entry, but may act by a similar mechanism. The β-helix motif may be used as an AFP structural motif in non-homologous proteins from other (non-fish) organisms as well.
A number of serum transport proteins are known to be evolutionarily related, including albumin, alpha-fetoprotein, vitamin D-binding protein and afamin [, , ]. Albumin is the main protein of plasma; it binds water, cations (such as Ca2+, Na+and K+), fatty acids, hormones, bilirubin and drugs - its main function is to regulate the colloidal osmotic pressure of blood. Alphafeto- protein (alpha-fetoglobulin) is a foetal plasma protein that binds various cations, fatty acids and bilirubin. Vitamin D-binding protein binds to vitamin D and its metabolites, as well as to fatty acids. The biological role of afamin (alpha-albumin) has not yet been characterised. The 3D structure of human serum albumin has been determined by X-ray crystallography to a resolution of 2.8A []. It comprises three homologous domains that assemble to form a heart-shaped molecule []. Each domain is a product of two subdomains that possess common structural motifs []. The principal regions of ligand binding to human serum albumin are located in hydrophobic cavities in subdomains IIA and IIIA, which exhibit similar chemistry. Structurally, the serum albumins are similar, each domain containing five or six internal disulphide bonds, as shown schematically below:+---+ +----+ +-----+| | | | | |xxCxxxxxxxxxxxxxxxxCCxxCxxxxCxxxxxCCxxxCxxxxxxxxxCxxxxxxxxxxxxxxCCxxxxCxxxx| | | | | |+-----------------+ +-----+ +---------------+This entry represents a conserved site that covers the three conserved cysteines at the end of the Serum albumin domain. It is built in such a way that it can detect all 3 repeats in albumin and human afamin, the first two in AFP and the first one in VDB and rat afamin.
Antifreeze proteins (AFPs) are a class of proteins that are able to bind to and inhibit the growth of macromolecular ice, thereby permitting an organism to survive subzero temperatures by decreasing the probability of ice nucleation in their bodies []. These proteins have been characterised from a variety of organisms, including fish, plants, bacteria, fungi and arthropods. This entry represents insect AFPs of the type found in spruce budworm, Choristoneura fumiferana.The structure of these AFPs consists of a left-handed β-helix with 15 residues per coil []. The β-helices of insect AFPs present a highly rigid array of threonine residues and bound water molecules that can effectively mimic the ice lattice. As such, β-helical AFPs provide a more effective coverage of the ice surface compared to the α-helical fish AFPs.A second insect antifreeze from Tenebrio molitor () also consists of β-helices, however in these proteins the helices form a right-handed twist; these proteins show no sequence homology to the current entry, but may act by a similar mechanism. The β-helix motif may be used as an AFP structural motif in non-homologous proteins from other (non-fish) organisms as well.
Antifreeze proteins (AFPs) are a class of proteins that are able to bind to and inhibit the growth of macromolecular ice, thereby permitting an organism to survive subzero temperatures by decreasing the probability of ice nucleation in their bodies []. These proteins have been characterised from a variety of organisms, including fish, plants, bacteria, fungi and arthropods. This entry represents insect AFPs of the type found in Tenebrio molitor (Yellow mealworm) and in Dendroides canadensis (Pyrochroid beetle).The structure of these AFPs consists of a right-handed β-helix with 12 residues per coil. Each 12 residue-repeat contains two cys residues that form a disulphide bridge. The β-helices of insect AFPs present a highly rigid array of threonine residues and bound water molecules that can effectively mimic the ice lattice. As such, β-helical AFPs provide a more effective coverage of the ice surface compared to the α-helical fish AFPs [].A second insect antifreeze from Choristoneura fumiferana (Spruce budworm) () also consists of β-helices, however in these proteins the helices form a left-handed twist; these proteins show no sequence homology to the current entry, but may act by a similar mechanism. The β-helix motif may be used as an AFP structural motif in non-homologous proteins from other (non-fish) organisms as well.
Antifreeze proteins (AFPs) are defined by their ability to bind ice and prevent it from growing. In this way they function in both freeze-resistance and freeze-tolerance strategies of organisms that live at sub-zero temperatures and require protection from ice growth. In fish, five AFP types have been described that are remarkably diverse in their 3D structures. They have completely dissimilar folds and no sequence homology. Type III AFPs found in eelpouts are 65-residue proteins with a compact globular fold formed from short β-strands, which presents a flat ice binding surface. These proteins are homologous to the C-terminal region of mammalian and prokaryotic sialic acid synthase (SAS; gene neuB), which has been called AFP-like domain []. The similarity is greatest in the protein core and the flat ice-binding region. SAS is involved in the condensation of phosphoenolpyruvate with N-acetylmannosamine derivatives to generate N-acetylneuraminic acid, an intermediate used for the sialylation of glycoconjugates. The function of the AFP-like domain, which is a β-clip fold [], in SAS is not known, but it has been proposed that it could be involved in sugar binding.
