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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.

CTNNBIP1 binds CTNNB1 and avoids interaction between CTNNB1 and TCF (T-cell transcription factor) family members. CTNNBIP1 is a negative regulator of the Wnt signaling pathway.

GDF-11 belongs to the bone morphogenetic protein (BMP) family and the TGF-beta superfamily. GDF-11 is a central developmental factor which controls muscular and neural development. In adults, GDF-11 encourages cardiac hypertrophy reverse by the revival of cardiomyocytes.

Maltose Binding Protein (MBP) is a part of the maltose/maltodextrin system of Eschericia coli bacteria, which is responsible for the uptake and efficient catabolism of maltodextrins. It is a complex regulatory and transport system involving many proteins and protein complexes.
Maltose binding protein MalE,MBP, is part of the maltodextrin transport system in E. coli. The maltodextrins diffuse through the LamB pore located in the outer membrane into the periplasm. The sugar is bound to MalE which prevents it to diffuse back outside. MalE passes the sugar to a complex of MalF and MalG in the cytoplasmic membrane where active tranport is mediated by the ATPase MalK. MBP molecular weight is 40,622 dalton. There are two domains in the protein with similar secondary structure (central pleated sheets are surrounded by helices) . The domains are connected by three bridges, between the domains is a deep groove in which the sugar is bound. All hydroxyl groups of the sugar are fixed by sidechains of the protein by hydrogen bonds. Some water molecules are part of the hydrogen bridge network.

S100A6 is a member of the S100 family of proteins containing 2 EF-hand calcium-binding motifs. S100 proteins are localized either in the cytoplasm or the nucleus of a wide range of cells. S100 proteins are involved in the regulation of a number of cellular processes such as cell cycle progression and differentiation. There are at least 13 members in the S100 gene family, which are located as a cluster on chromosome 1q21.
S100A6 may function in stimulation prolactin secretion, and exocytosis. Chromosomal rearrangements and altered expression of the S100A6 gene are implicated in melanoma.

Adipocyte fatty acid binding protein FABP4 is a 15 kDa member of the intracellular fatty acid binding protein (FABP) family, which is known for the ability to bind fatty acids and related compounds (bile acids or retinoids) in an internal cavity. FABP4 is expressed in a differentiation-dependent fashion in adipocytes and is a critical gene in the regulation of the biological function of these cells.
In mice, targeted mutations in FABP4 provide significant protection from hyperinsulinemia and insulin resistance in the context of both dietary and genetic obesity. Adipocytes obtained from FABP4-deficient mice also have reduced efficiency of ipolysis in vitro and in vivo, and these mice exhibited moderately improved systemic dyslipidemia. Recent studies also demonstrated FABP4 expression in macrophages upon differentiation and activation. In these cells, FABP4 modulates inflammatory responses and cholesterol ester accumulation, and total or macrophage-specific FABP4 deficiency confers dramatic protection against atherosclerosis in the apoE-/- mice. These results indicate a central role for FABP4 in the development of major components of the metabolic syndrome through its distinct actions in adipocytes and macrophages.

PTB domain-containing engulfment adapter protein 1 (GULP1) is an evolutionarily conserved adaptor protein essential for efficient phagocytosis of apoptotic cells by phagocytes. Furthermore, GULP1 helps modulate cellular glycosphingolipid and cholesterol transport. In addition, GULP1 may have a role in the internalization and endosomal trafficking of various LRP1 ligands, such as PSAP. Increased cytoplasmic levels of GULP1 are linked with increases in cellular levels of GTP-bound ARF6.

ULBP1 together with at least ULBP2 and ULBP3, is ligand for the NKG2D receptor. ULBPs stimulate various signaling pathways in primary NK cells, which result in cytokines and chemokines production. In CMV infected cells, ULBP1 cooperates with soluble CMV glycoprotein UL16 to inhibit the interaction with the NKG2D receptor providing a mechanism by which CMV infected cells escape the immune system. Additionally, UL16 retains ULBP1 to the ER and cis-Golgi apparatus to prevent it from reaching cell surface.

CRCP is a ubiquitous coupling protein for the calcitonin gene-related peptide and adrenomedullin receptors. CRCP controls ligand sensitivity in several tissues and has DNA-directed RNA polymerase activity, catalytic activity and calcitonin receptor activity.

GroEL, HSP60 is a chaperonin located in the mitochondria which is responsible for the transportation & refolding of proteins from the cytoplasm directly into the mitochondrial matrix. GroEL is regulated by the HSP10 cochaperonin, which is a single heptameric protein ring having a molecular mass of 10 kDa which form a unique complex with HSP60. HSP10, GroES coordinates the ATPase activity of the HSP60 subunits in order to allow the release of bound polypeptide in a manner that is productive for its correct folding.

S100A3 is part of S100 family of proteins containing 2 EF-hand calcium-binding motifs. S100 proteins are localized in the cytoplasm/nucleus of a broad range of cells, and takes part in the regulation of several cellular processes such as cell cycle progression and differentiation. S100A3 has the largest number of cysteines of all S100 proteins. S100A3 has high affinity for Zinc, and is widely expressed in human hair cuticle.

Cytohesin 3 (CYTH3) belongs to the PSCD family, whose members have identical structural organization which consists of an N-terminal coiled-coil motif, a central Sec7 domain, and a C-terminal pleckstrin homology (PH) domain, and seem to mediate the regulation of protein sorting and membrane trafficking. CYTH3 is involved in the regulation of Golgi structure and function, and it might have a physiological role in regulating ADP-ribosylation factor protein 6 (ARF) functions, in addition to acting on ARF1.

FABP1 (Fatty acid binding protein1) encodes the fatty acid binding protein found in liver. FABP1 is composed of ten antiparallel beta strands that form a barrel with a bigger binding pocket than the other FABPs allowing it to accommodate two fatty acid. This protein binds free fatty acids and their coenzyme A derivatives, bilirubin, and some other small molecules in the cytoplasm; it may be involved in intracellular lipid transport and metabolism.

Antigen 85A is a member of the antigen 85 complex (Antigen 85A, B, C). The enzymes of the antigen 85 complex have mycolyltransferase activity and catalyze the synthesis of the very rich glycolipid of the mycobacterial cell wall, the cord factor (trehalose 6,6'-dimycolate, TDM). The cord factor is vital for the integrity of the mycobacterial cell wall and pathogenesis of the bacillus. TDM is synthesized from two molecules of trehalose-6'-monomycolate (TMM) by Antigen 85A.

GDNF family receptor alpha-1 (GFRA1) belongs to the GDNF receptor family. GFRA1 is a glycosyl-phosphatidylinositol(GPI)-linked cell surface receptor for both Glial cell line-derived growth factor (GDNF), neurturin (NTN), and mediates activation of the RET tyrosine kinase receptor. The GFRA1 protein is a potent survival factor for central and peripheral neurons, and is vital for the development of kidneys and the enteric nervous system.

Sex-hormone-binding globulin (SHBG) is a beta-globulin which specifically binds steroid hormones; it is involved in the transport of sex steroids in plasma. The main site of SHBG synthesis is assumed to be the hepatocytes. The production of SHBG is regulated by androgen/estrogen balance, thyroid hormones, insulin and dietary factors, among others. The concentration of SHBG is a key factor regulating their distribution between protein-bound and free states. SHBG concentration determination is primarily significant in the evaluation of mild disorders of androgen metabolism and it allows detection of women with hirsutism who are likely to react to estrogen therapy. Testosterone/SHBG-ratios correlate well with both measured and calculated values for free testosterone thus aid to distinguish between subjects with excessive androgen activity and normal individuals. SHBG gene polymorphisms are linked with polycystic ovary syndrome and type 2 diabetes mellitus.

EIF4EBP2 belongs to the eukaryotic translation initiation factor 4E binding protein family. Even though EIF4EBP2 protein binds eIF4E and inhibits translation initiation, growth factors can release this inhibition by a phosphorylation-dependent disruption. EIF4EBP2 mediates the regulation of protein translation by hormones, growth factors and other stimuli that signal through the MAP kinase pathway. Regulation of this protein is associated to cell proliferation, cell differentiation and viral infection.

CRABP1 is a member of special carrier proteins for members of the vitamin A family. It is believed that CRABP1 has an essential role in retinoic acid-mediated differentiation and proliferation processes. Though, CRABP1 is structurally similar to the cellular retinol-binding proteins, it binds only retinoic acid at specific sites within the nucleus, which may contribute to vitamin A-directed differentiation in epithelial tissue. CRABP1 is constitutively expressed and is thought to have different functions in the cell than the related CRABP2. CRABP1 forms a beta-barrel structure which accommodates hydrophobic ligands in its interior.
Loss of CRABP1 function as a result of hypermethylation of its promoter leads to pathogenesis of papillary thyroid carcinoma. Furthermore, frequent methylation-associated silencing of CRABP1 is linked to esophageal squamous-cell carcinoma.

EIF4EBP1 (eukaryotic translation initiation factor 4E-binding protein 1) belongs to a family of translation repressor proteins. EIF4EBP1 regulates eIF4E (eukaryotic translation initiation factor 4E) activity by preventing its assembly into the eIF4F complex and mediates the regulation of protein translation by hormones, growth factors and other stimuli that signal through the MAP kinase and mTORC1 pathways. EIF4EBP1 is phosphorylated in response to various signals including UV irradiation, resulting in its dissociation from eIF4E and activation of mRNA translation. EIF4EBP1 C-terminus has domains which control function and phosphorylation. EIF4EBP1 has a role in progression of breast neoplasms through cell signaling.

Cytosolic Fe-S cluster assembly factor NUBP1 isoform 1 (NUBP1) is Involved in the regulation of centrosome duplication similarity. NUBP1 is a component of the cytosolic iron-sulfur (Fe/S) protein assembly (CIA) machinery. NUBP1 is necessary for maturation of extra mitochondrial Fe-S proteins. The NUBP1-NUBP2 heterotetramer constructs a Fe-S scaffold complex, mediating the de novo compilation of a Fe-S cluster and its transfer to target apoproteins.

GSTP1 is a polymorphic gene encoding active, functionally different GSTP1 variant proteins that are believed to function in xenobiotic metabolism and have a part in susceptibility to cancer, and other diseases. GSTP1 is a glutathione S-transferase belonging to the pi class. GST family enzymes play a significant role in detoxification by catalyzing the conjugation of many hydrophobic and electrophilic compounds with reduced glutathione. Based upon the biochemical, immunologic and structural properties of the soluble GSTs they are grouped into 4 main classes: alpha, mu, pi, and theta. The GSTP1 enzyme acts by catalyzing the reaction of glutathione with an acceptor molecule to form a Sulfur-substituted glutathione. The reactions employing glutathione contribute the transformation of a broad range of electrophiles, including reactive products of lipid, protein, carcinogens, therapeutic drugs, environmental toxins, and products of oxidative stress.
The GSTP1 inactivation through CpG hypermethylation is frequent in pituitary adenomas and may be a factor in aggressive pituitary tumor behavior. GSTP1 is may be a transcriptional target of the p53 tumor suppressor gene. Single-nucleotide polymorphism in GSTP1 is linked to modified protein binding, which influence GSTP1's contribution to carcinogen and drug metabolism, and possibly disease pathogenesis and/or drug response. GST-pi might have central roles in proliferation of androgen-independent human prostate cancer cells.

GRB2 is widely expressed and binds the EGFR and contains one SH2 domain and two SH3 domains which form a complex formation with proline-rich regions of other proteins, and its SH2 domain binds tyrosine phosphorylated sequences. GRB2 is related to the Sem5 gene of C.elegans, which is takes part in the signal transduction pathway. GRB2 is an adaptor protein that provides an important link between cell surface growth factor receptors and the Ras signaling pathway. Inhibition of GRB2 activity damages developmental processes in a variety of organisms and blocks transformation and proliferation of different cell types.