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Osteocrin is a recently identified secreted protein expression of which was only detected in bone, peaking just after birth and decreasing markedly with age. A 1280-bp mRNA encodes osteocrin producing a mature protein of 103 amino acids with a molecular mass of 11.4 kDa. In primary osteoblastic cell cultures osteocrin expression coincided with matrix formation then decreased in very mature cultures. Treatment of cultures with 1,25-dihydroxyvitamin D3 resulted in a rapid dose- dependent down-regulation of osteocrin expression, suggesting direct regulation. Chronic treatment of primary cultures with osteocrin-conditioned media inhibited mineralization and reduced osteocalcin and alkaline phosphatase expression. These results suggest that osteocrin represents a novel, unique vitamin D-regulated bone-specific protein that appears to act as a soluble osteoblast regulator.

Streptavidin is a tetrameric protein secreted by Streptomyces avidinii which binds firmly to biotin. Streptavidin is widely used in molecular biology through its unique high affinity for the vitamin biotin. The dissociation constant (Kd) of the biotin-streptavidin complex is about ~10-15 mol/L. The strong affinity recognition of biotin and biotinylated molecules has made streptavidin one of the most important components in diagnostics and laboratory kits. The streptavidin/biotin system has one of the biggest free energies of association of yet observed for noncovalent binding of a protein and small ligand in aqueous solution (K_assoc = 10**14). The complexes are also extremely stable over a wide range of temperature and pH.

Streptavidin is a tetrameric protein secreted by Streptomyces avidinii which binds firmly to biotin. Streptavidin is widely used in molecular biology through its unique high affinity for the vitamin biotin. The dissociation constant (Kd) of the biotin-streptavidin complex is about ~10-15 mol/L. The strong affinity recognition of biotin and biotinylated molecules has made streptavidin one of the most important components in diagnostics and laboratory kits. The streptavidin/biotin system has one of the biggest free energies of association of yet observed for noncovalent binding of a protein and small ligand in aqueous solution (K_assoc = 10**14). The complexes are also extremely stable over a wide range of temperature and pH.

FABP6 also called ileal fatty acid binding protein, is part of the small family of highly conserved, cytoplasmic proteins that bind long-chain fatty acids and other hydrophobic ligands. FABP6 cytosolic protein binds bile acid. FABP6 plays a role in fatty acid uptake, transport, and metabolism. FABP6 stimulates gastric acid and pepsinogen secretion. Seems to be able to bind to bile salts and bilirubins. FABP6 expression is restricted in the small intestine to the ileum where it is involved in the enterohepatic circulation of bile acids. Alternate transcription promoters generate 2 transcript variants, encoding a 128 aa and a 177 aa residue protein. Human FABP6 isoform 2 contains 128 amino acid residues and is acetylated on Ala2. FABP6 binds together fatty acids and bile acids and is directly involved in fatty acid transport and metabolism.

Capping Protein (Actin Filament) Muscle Z-Line, Alpha 2 also known as CAPZA2 belongs the F-actin capping protein alpha subunit family. It is the alpha subunit of the barbed-end actin binding protein Cap Z. By capping the barbed end of actin filaments, Cap Z regulates the growth of the actin filaments at the barbed end. Among the diseases associated with CAPZA2 are endocarditis, and cervicitis.

Ketosamine-3-kinase (FN3KRP) catalyzes the phosphorylation of psicosamines and ribulosamines compared to the adjacent gene which encodes a highly analogous enzyme, fructosamine-3-kinase that has different substrate specificity. The activity of both enzymes may cause deglycation of proteins to reinstate their function. A high concentration of glucose can result in non-enzymatic oxidation of proteins by reaction of glucose and lysine residues (glycation). The proteins altered in this way, are less active or functional.

Frataxin is a mitochondrial iron binding protein that is part of the FRATAXIN family. Frataxin functions in regulating mitochondrial iron transport and respiration. The expansion of intronic trinucleotide repeat GAA results in Friedreich ataxia. Frataxin plays a role in iron homeostasis. Frataxin is an anti-apoptotic protein which prevents mitochondrial damage and reactive oxygen species (ROS) production.

Polymerase (DNA Directed), Epsilon 3, also know as POLE3, is a histone-fold protein which interacts with other histone-fold proteins to bind DNA in a sequence-independent manner. These histone-fold protein dimers merge into larger enzymatic complexes for DNA transcription, replication, and packaging.

PPIF is a part of the peptidyl-prolyl cis-trans isomerase (PPIase) family. PPIF accelerates the folding of proteins. It catalyzes the cis-trans isomerization of proline imidic peptide bonds in oligopeptides. PPIF is key component of the mitochondrial permeability transition pore in the inner mitochondrial membrane. Activation of this pore is thought to be involved in the induction of apoptotic and necrotic cell death.

CETN3 comprises of 4 EF-hand calcium binding domains, and is a part of the centrin protein family. CETN3 protein is widely expressed cytoskeletal components that demonstrate increased expression during cell differentiation. CETN3 takes part in centrosome reproduction.

CFL2 protein is a member of the actin-binding proteins ADF family which contains 1 ADF-H domain. Cofilin is a broadly distributed intracellular actin-modulating protein which binds and depolymerizes filamentous F-actin and inhibits the polymerization of monomeric G-actin in a pH-dependent manner. Defects in the CFL2 gene are the cause of nemaline myopathy type 7 (NEM7).

RGS19 is a member of RGS (regulator of G protein signaling) family and negatively regulates G protein coupled receptor signaling. RGS19 protein specifically cooperates with heterotrimeric GTP-binding protein G alpha i3 (GAI3).

E3 ubiquitin-protein ligase RNF181 (RNF181) accepts ubiquitin from an E2 ubiquitin-conjugating enzyme in the thioester form and subsequently directly transfers the ubiquitin to targeted substrates. RNF181 is widely expressed, with the highest levels in the liver and heart and the lowest levels in the brain and skeletal muscle. RNF181 is also expressed in platelets (at protein level).

Ankyrin Repeat Family A2, also known as ANKRA2 contains 5 ANK repeats. ANKRA2 assist endocytosis by linking megalin to components of the cytoskeleton or endocytic machinery.

NECTIN3, also known as Nectin Cell Adhesion Molecule 3, is part of the nectin family. NECTIN3 is intended to initiate cell-cell adhesion to stimulate cell attachment and to allow subsequent formation of JAM-and cadherin-based intercellular junctions. NECTIN3 induces endocytosis-mediated down-regulation of PVR from the cell surface, which results in reduction of cell movement & proliferation. Following Nectin-3 activity adds strength to the junction through trans-interaction with various molecules.

"Epiregulin is part of the EGF family. Epiregulin functions as a ligand of EGFR, as well as a ligand of most members of the ERBB (v-erb-b2 oncogene homolog) family of tyrosine-kinase receptors.Epiregulin is expressed mostly in the placenta and peripheral blood leukocytes and in specific carcinomas of the bladder, lung, kidney and colon. Epiregulin stimulates the proliferation of keratinocytes, hepatocytes, fibroblasts and vascular smooth muscle cells. Epiregulin inhibits the growth of several tumor-derived epithelial cell lines. Human Epiregulin is initially synthesized as a glycosylated 19.0 kDa transmembrane precursor protein, which is processed by proteolytic cleavage to produce a 6.0 kDa mature secreted sequence."

TFPI2 takes part in the regulation of plasmin-mediated matrix remodeling. Inhibits trypsin, plasmin, factor VIIa/tissue factor and weakly factor Xa. TFPI2 doesn’t have any influence on thrombin.

Cyclophilin-D is a member of the peptidyl-prolyl cis-trans isomerase (PPIase) family. PPIases catalyze the cis-trans isomerization of proline imidic peptide bonds in oligopeptides and speeds up the protein folding. Cyclophilin-D possess PPIase activity and binds to the immunosuppressant cyclosporin-A. Cyclophilin-D is very well known that its overexpression suppresses the apoptosis in cancer cell. Cyclophilin-D suppresses apoptotic cell death by the use of mitochondrial hexokinase-2 dependent mechanism in cancer cells.

Leptin takes an important part in the regulation of energy balance and body weight control.After entering the circulation, Leptin binds LEPRwhich results in the activation of several major signalling pathways. In the hypothalamus Leptin acts as an appetite-regulating factor that induces a decrease in food intake and an increase in energy consumption and also regulates bone mass and secretion of hypothalamo-pituitary-adrenal hormones. In the periphery, increases basal metabolism, regulates pancreatic beta-cell function and insulin secretion and affects innate and adaptive immunity.

SPARC, an acronym for “secreted protein, acidic and rich in cysteine”, is also known as osteonectin or BM-40. It is the founding member of a family of secreted matricellular proteins with similar domain structure. The 303 amino acid, 43 kDa protein contains a 17 aa signal sequence, an N-terminal acidic region that binds calcium, a follistatin domain containing Kazal-like sequences, and a C-terminal extracellular calcium (EC) binding domain with two EF-hand motifs. SPARC is produced by fibroblasts, capillary endothelial cells, platelets and macrophages, especially in areas of tissue morphogenesis and remodeling. SPARC shows context-specific effects, but generally inhibits adhesion, spreading and proliferation, and promotes collagen matrix formation. For endothelial cells, SPARC disrupts focal adhesions and binds and sequesters PDGF and VEGF. SPARC is abundantly expressed in bone, where it promotes osteoblast differentiation and inhibits adipogenesis.

Alpha crystallins are composed of two gene products ; alpha-A and alpha-B, for acidic and basic, respectively. Alpha crystallins can be induced by heat shock and are members of the small heat shock protein(sHSP also known as the HSP20). They act as molecular chaperones and hold them in large soluble aggregates. These heterogeneous aggregates consist of 30-40 subunits; the alpha-A and alpha-B subunits have a 3:1 ratio, respectively. Two additional function of a-crystallins are an autokinase activity and participation in the intracellular architecture. The expression of alpha-A is preferentially restricted to the lens cell.

Prorelaxin H2 (RLN2) is a member of the insulin gene superfamily. This family which is produced by the ovary, targets the mammalian reproductive system to ripen the cervix, elongate the pubic symphysis and inhibit uterine contraction. It may also have other roles in boosting sperm motility, regulating blood pressure, controlling heart rate and releasing oxytocin and vasopressin. RLN2 is a peptide hormone linked to several therapeutically relevant physiological effects, including regulation of collagen metabolism and multiple vascular control pathways. The active form of the RLN2 protein consists of an A chain and a B chain linked by disulfide bonds.

Peptidyl-prolyl cis-trans isomerase F, mitochondrial (Cyclophilin-F) accelerates the folding of proteins. Cyclophilin-F catalyzes the cis-trans isomerization of proline imidic peptide bonds in oligopeptides and involved in regulation of the mitochondrial permeability transition pore (mPTP). Cyclophilin-F, in cooperation with mitochondrial TP53, is involved in activating oxidative stress-induced necrosis. Cyclophilin-F is also involved in modulation of mitochondrial membrane F1F0 ATP synthase activity and regulation of mitochondrial matrix adenine nucleotide levels. Furthermore, Cyclophilin-F has anti-apoptotic activity independently of mPTP and in cooperation with BCL2 inhibits cytochrome c-dependent apoptosis.