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Maltose Binding Protein is a member of the maltose/maltodextrin system of E.Coli, which is accountable for the uptake and efficient catabolism of maltodextrins. The maltose/maltodextrin is a complex regulatory and transport system involving many proteins and protein complexes. MBP elevates the yield of its fusion partner in many cases and is often able to promote the solubility of polypeptides to which it is fused.

ERCC1 polypeptide is essential for nucleotide excision repair (NER) of damaged DNA and is homologous to Saccharomyces cerevisiae RAD10, which takes part in repair and mitotic intra-chromosomal recombination. NER mechanism includes dual incisions on both sides of the damage catalyzed by two nucleases. In mammalian cells XPG cleaves 3' of the DNA lesion while the ERCC1-XPF complex makes the 5' incision.

Chitinase is a digestive enzyme which breaks down glycosidic bonds in chitin. Due to chitin being a component of the cell walls of fungi and exoskeletal elements of some animals (including worms and arthropods), chitinases are usually found in organisms that either need to remake their own chitin or to dissolve and digest the chitin of fungi or animals. Chitinivorous organisms include many bacteria genuses such as Aeromonas, Bacillus, Vibrio, among others, which may be pathogenic or detritivorous. Chitinase expression is mediated by the NPR1 gene and the salicylic acid pathway, both of which are involved in resisting fungal and insect attack. Human chitinases appear in gastric juices. They are likely to be digestive chitinases, for catabolic activity. Chitinase activity is identified systemically in humans, in the blood, and possibly cartilage. Chitinase has been related to allergies, asthma in particular has been linked to enhanced chitinase expression levels, also dust mites and mold spores which are both chitin covered.

EEF1A1 is an isoform of the alpha subunit of the elongation factor-1 complex, which is responsible forthe enzymatic release of aminoacyl tRNAs to the ribosome. EEF1A1 is expressed in brain, placenta, lung, liver, kidney, and pancreas, and the other isoform (alpha 2) is expressed in brain, heart and skeletal muscle. EEF1A1 is recognized as an autoantigen in 66% of patients with Felty syndrome. EEF1A1 has multiple copies on numerous chromosomes, part of them, if not all, symbolize different pseudogenes. Among the diseases associated with EEF1A1 are tinea nigra and andcervical cancer.

Complement C4c is a degradation product of C4b which is cleaved by C4b/C3b inactivator to yield C4d and C4c.
Complement C4c interacts with C1 and C2 to form C3 convertase of the classic activation pathway. Systemic lupus erythematosus (SLE) is often associated with congenital C4 deficiency. Reduced levels of components of the classic pathway (C1, C2, C4, C3) are common after such activation, e.g. in SLE, acute serum sickness and conditions associated with circulating immune complexes.

PRCP is a plasma protein which takes part in the cleavage of C-terminal amino acids linked to proline in proteinfor example angiotensin-2 & 3 at acidic pHenvironment rather than at neutral pHwhich exhibit less activity. This cleavage is important since Angiotensin-2 takes part in regulation of blood pressure & electrolyte balance which is essential to hypertension.

C3 is central to the activation of all 3 pathways of complement activation. Initiation of each pathway generates proteolytic enzyme complexes which binds the target surface. These enzymes cleave a peptide bond in C3 releasing the anaphylatoxin C3a and activating C3b. Most of the C3 activated during complement activation never attaches to the surface due to its thioester reaction with water forming fluid phase C3b which is rapidly inactivated by factors H and I forming iC3b. Surface-bound C3b is necessary in all 3 pathways for efficient activation of C5 and formation of C5b-9 complexes that lyse the target cell membrane.

Casein Kinase 2 also called CK2 (also called PKCK2) is a ubiquitous Ser/Thr kinase expressed in all eukaryotes. CK2 is a tetramer composed of two catalytic kinase domains, alpha subunits, and two identical regulatory beta subunits. It has been implicated in cell cycle control, DNA repair, regulation of the circadian rhythm, and other cellular processes. The beta subunit itself does not have kinase activity, but confers stability to the CK2 alpha subunit and is involved in activity and substrate specificity.

Phosphopantothenate-cysteine ligase (PPCS) catalyzes the first step in the biosynthesis of coenzyme A (CoA) from pantothenic acid (vitamin B5), which is a vital universal pathway in prokaryotes and eukaryotes. PPCS, being one of the last enzymes in this pathway, converts phosphopantothenate to phosphopantothenoylcysteine.

Carboxypeptidase-E (CPE ) is a carboxypeptidase that cleaves C-terminal amino acid residues and is involved in the biosynthesis of peptide hormones and neurotransmitters. CPE is a peripheral membrane protein. CPE specifically connects regulated secretory pathway proteins, including prohormones, but constitutively secreted proteins. Mutations in CPE are implicated in type II diabetes.

Neuron-specificenolase also caled NSE is a glycolytic isoenzyme which is situated in central and peripheral neurons and neuroendocrine cells. Enolase-2 is released into the CSF when neural tissue is injured. Neoplasms derived from neural or neuroendocrine tissue release Enolase-2 into the blood. Enolase-2 is a useful substance that has been detected in patients with certain tumors, such as neuroblastoma, small cell lung cancer, medullary thyroid cancer, carcinoid tumors, pancreatic endocrine tumors, and melanoma. ENO2 is 1 of the 3 enolase isoenzymes found in mammals. ENO2 isoenzyme, is found in mature neurons and cells of neuronal origin. An exchange from alpha enolase to gamma enolase occurs in neural tissue during development in rats and primates.

CPPED1 which is a part of the metallophosphoesterase superfamily takes part in glucose uptake by adipocytes. CPPED1 binds two divalent metal cations and is transactivated by the great envelope protein of the hepatitis B virus.

Cystatins are a superfamily of cysteine proteinase inhibitors found in both plants and animals. They comprise a group of proteinase inhibitors, widely distributed in tissues and body fluids, and form tight complexes with cysteine proteases such as cathepsin B, H, L and S. Cystatin C, a secreted molecule of this family, is of interest from biochemical, medicine and evolutionary points of view. Cystatin C, with molecular weight of 13260 Da, is composed of 120 amino acids, lacks carbohydrate and has two disulfide bridges located near the carboxyl terminus. Cystatin C is increased in patients with malignant diseases, and is related to the insufficiency of renal function and appears to be a better marker than creatinine. On the other hand, low levels of cystatin C involve cause the breakdown of the elastic laminae and, subsequently, the atherosclerosis and abdominal aortic aneurysm.

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.

Epidermal growth factor has a profound effect on the differentiation of specific cells in vivo and is a potent mitogenic factor for a variety of cultured cells of both ectodermal and mesodermal origin. The EGF precursor is believed to exist as a membrane-bound molecule which is proteolytically cleaved to generate the 53-amino acid peptide hormone that stimulates cells to divide. EGF stimulates the growth of various epidermal and epithelial tissues in vivo and in vitro and of some fibroblasts in cell culture.

TCEB1 (elongin C) is a subunit of elongin, which is a common transcription elongation factor that increases the RNA polymerase II transcription elongation past template encoded arresting sites. The SIII complex is comprised of elongins A/A2, B and C. The SIII complex activates elongation by RNA polymerase II by curbing transient pausing of the polymerase at numerous sites within transcription units. Elongin A acts as the transcriptionally active component of the SIII complex, while elongins B and C are regulatory subunits. Elongin A2 is specifically expressed in the testis, and able to forming a stable complex with elongins B and C. The VHL (von Hippel-Lindau) tumor suppressor protein binds to elongins B and C, and thus inhibits transcription elongation.

Cystatins are a superfamily of cysteine proteinase inhibitors found in both plants and animals. They comprise a group of proteinase inhibitors, widely distributed in tissues and body fluids, and form tight complexes with cysteine proteases such as cathepsin B, H, L and S. Cystatin C, a secreted molecule of this family, is of interest from biochemical, medicine and evolutionary points of view. Cystatin C, with molecular weight of 13260 Da, is composed of 120 amino acids, lacks carbohydrate and has two disulfide bridges located near the carboxyl terminus. Cystatin C is increased in patients with malignant diseases, and is related to the insufficiency of renal function and appears to be a better marker than creatinine. On the other hand, low levels of cystatin C involve cause the breakdown of the elastic laminae and, subsequently, the atherosclerosis and abdominal aortic aneurysm.

C-type lectin domain family 4, member E, also known as CLEC4E is a C-type lectin receptor expressed through a wide range of antigens which presents cells including macrophages, neutrophils, dendritic cells as well as B cells; Furthermore, a variety of stimuli including stress are acknowledged to induce the expression of CLEC4E.

Avidin is a tetrameric protein of 4 identical subunits (homotetramer) each of which can bind to biotin with a high degree of affinity and specificity. Avidin molecular weight in its tetrameric form is estimated to be between 66-69 kDa. Avidin is produced in the oviducts of birds, reptiles and amphibians and is subsequently deposited in the whites of their eggs. In the chicken egg white, avidin makes up roughly 0.05% of total protein (approximately 1.8 mg per egg). 10% of Avidin’s molecular weight is ascribed to carbohydrate content which is composed of four to five mannose and three N-acetylglucosamine residues. Avidin has at least three distinctive oligosaccharide structural type which are similar in structure and composition. The dissociation constant (KD) of avidin is approximately 10-15M, making it one of the strongest known non-covalent bonds.

PCYT2 is a member of the cytidylyltransferase family. PCYT2 is an enzyme which catalyzes the formation of CDP-MEA from CTP and phospho MEA in the Kennedy pathway of phospholipid synthesis. PCYT2 has the strongest expression in the liver, heart, and skeletal muscle.

Glycophorin C, also known as GYPC, is an integral membrane glycoprotein. GYPC is a minor species which is carried by human erythrocytes, however plays an important role in regulating the mechanical stability of red cells. Numeral glycophorin C mutations have been described. The Gerbich and Yus phenotypes are due to deletion of exon 3 & 2, respectively. The Webb & Duch antigens, also identified as glycophorin D, result from single point mutations of the glycophorin C gene. The glycophorin C protein has very slight homology with glycophorins A & B.

Tubulin folding cofactor C (TBCC) is a member of the TBCC family. TBCC has a role in the control of centrosome and Golgi apparatus positioning, with effects on cell shape and cell migration. Cofactor C is 1 of 4 proteins (cofactors A,D,E and C) engaged in the pathway leading to properly folded b-tubulin from folding intermediates. Cofactor E attaches to the cofactor D/beta-tubulin complex; their interaction with cofactor C subsequently causes the release of beta-tubulin polypeptides which are bound to the native state.

PPP1CC is vital for cell division and takes part in the regulation of protein synthesis, muscle contractility and glycogen metabolism. Additionally, PPP1CC has a role in long-term synaptic plasticity and regulation of ionic conductance, and has a significant role in dephosphorylating substrates such as the postsynaptic density-associated Ca2+/calmodulin dependent protein kinase II.