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HSP90B1 is an abundant molecular chaperone resident endoplasmic reticulum (ER) lumenal stress protein which is part of the Hsp90 family. HSP90B1 is involved in maintaining protein homeostasis in the secretory pathway as well as functioning in the intracellular trafficking of peptides from the extracellular space to the MHC class I antigen processing pathway of antigen presentation cells. HSP90B1 has key roles in signal transduction, protein folding, protein degradation, and morphologic evolution. HSP90B1 protein associates with numerous cochaperones and involved in folding of newly synthesized proteins or stabilizing and refolding denatured proteins after stress. HSP90B1 is highly expressed in human gastric carcinoma BGC-823 cells during the whole cell cycle.

HSP27 or Estrogen-Regulated 24K proteinis a part of the mammalian small heat shock protein family. The protein is expressed constitutively in many tissues and its expression is increased to high levels after different types of stress including high temperatures, toxic metals, drugs and oxidants. Furthermore, Hsp27 is phosphorylated in vivo on three phosphorylation sites (Ser15, Ser78 and Ser82) by protein kinases including MAPKAP kinase 2 and the stress-activated protein kinase SAPK2 (p38).

HRSP12 (UK114) is an endoribonuclease found mainly in the human adult kidney and liver, and which is responsible for inhibiting translation by cleaving mRNA. HRSP12 cleaves phosphodiester bonds only in single-stranded RNA. HRSP12 may be an important biomarker for heptatic carcinoma.

HSPA6 is a distinctive member of the human Hsp70 chaperone that takes part in cellular processes such as protein trafficking, folding, and prevention of aggregation. HSPA6 is strictly stress-inducible, having little or no basal expression levels in most cells. HSPA6 and HSP72 are are involved in cell survival of proteotoxic stress.

SERPINH1 is part of the serpin superfamily of serine proteinase inhibitors. SEPINH1 expression is induced by heat shock. HSP47 localizes to the endoplasmic reticulum lumen and binds collagen therefore it is a molecular chaperone which takes part in the maturation of collagen molecules, facilitating the folding and assembly of procollagen molecules, retaining unfolded molecules within the ER, and assisting the transport of correctly folded-molecules from the ER to Golgi apparatus. Autoantibodies to HSP47 protein have been found in rheumatoid arthritis. SERPINH1 binds specifically to collagen and acts as a chaperone in the biosynthetic pathway of collagen.

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.

DnaJ homolog subfamily B member 6 (DNAJB6) belongs to the DNAJ protein family. The DNAJ family members are characterized by a highly conserved amino acid stretch known as the 'J-domain' and function as one of the two major classes of molecular chaperones involved in a wide range of cellular events, such as protein folding and oligomeric protein complex assembly. DNAJB6 may also play a role in polyglutamine aggregation in specific neurons.

Once Chinese hamster K12 cells are starved from glucose, the synthesis of GRP (glucose-regulated protein) expressed. HSPA5 also called BiP, is part of the HSP70 family and plays a role in the folding and assembly of proteins in the endoplasmic reticulum. HSPA5 plays a key role in monitoring protein transport through the cell.
HSPA5 is a stress response protein which is induced by agents or conditions that adversely affect endoplasmic reticulum function. HSPA5 is crucial for the proper glycosylation, folding as well as for the maintenance of cell homeostasis and the prevention of apoptosis. HSPA5 is differentially expressed in the dorsolateral prefrontal cortex from patients with schizophrenia. HSPA5 guides posttranslational hepatitis B virus large envelope protein import into the mammalian ER. HSPA5 actively regulates multiple malignant phenotypes, including cell growth, migration, and invasion.

DnaK, originally identified for its DNA replication by bacteriophage l in E. coli is the bacterial HSP-70 chaperone. This protein is involved in the folding and assembly of newly synthesized polypeptide chains and in preventing the aggregation of stress-denatured proteins.
DnaK(amino acids1-384) is N-terminal ATPase domain and ATP bound to the ATPase domain induces a conformational change in the substrate binding domain (residues 385-638). The protein coding region of the ATPase domain of DNAK (amino acids 1-384) was amplified by PCR and cloned into an E. coli expression vector. The ATPase domain of DNAK was purified to apparent homogeneity by using conventional column chromatography techniques.

HSP104 is a molecular chaperone required for stress tolerance and for maintenance of [psi(+)] prions in the budding yeast Saccharomyces cerevisiae. Hsp104 can protect yeast cells against high temperature and high concentration of ethanol but mutation studies have shown this protein is not required for normal growth. Hsp104 was cloned into an E. coli expression vector and was purified to apparent homogeneity by using conventional column chromatography techniques.

STIP1 is an adaptor protein that mediates the functions of HSP70 & HSP90 in protein folding. STIP1 supports the transfer of proteins from HSP70 to HSP90 by binding together HSP90 and substrate-bound HSP70. STIP1 stimulates the ATPase activity of HSP70 and inhibits the ATPase activity of HSP90, suggesting that it regulates both the conformations and ATPase cycles of these chaperones. STIP1 genetic variations are involved in regulating corticosteroid response in asthmatic subjects with reduced lung function.

DNAJC19 is part of a complex involved in the ATP-dependent transport of transit peptide-containing proteins from the inner cell membrane to the mitochondrial matrix. DNAJC19 is a single-pass membrane protein which contains a J domain and is localized to the inner membrane of the mitochondrion. Expressed ubiquitously, DNAJC19 acts as a component of the mitochondrial DNAJC19 complex that is responsible for the ATP-dependent translocation of select proteins from the inner mitochondrial membrane to the mitochondrial matrix. Defects in the DNAJC19 gene are the cause of 3-methylglutaconic aciduria type 5 (MGA5), otherwise known as dilated cardiomyopathy with ataxia (DCMA).

DnaJ (Hsp40) Homolog, Subfamily C, Member 27 (DNAJC27) which contains one J domain is a part of the small GTPase superfamily. DNAJC27 is a GTPase which activates the MEK/ERK pathway and induces cell transformation when overexpressed.

CRAHSP1 is a serine phosphoprotein initially identified as a physiological substrate for the Ca2+-calmodulin regulated protein phosphatase calcineurin (PP2B). CRAHSP1 interacts with the STYX/dead phosphate protein in developing spermatids and is a paralog of the brain-specific mRNA-binding protein PIPPIN. It is believed to have a common role in calcium-mediated signal transduction resulting from phosphorylation on serine residues.

GroES protein is the co-chaperonin of GroES in E.coli and assists protein folding. GroEL mediated folding requires the co-chaperonin GroES which is essential for viability. GroES is composed of a single heptameric ring of 10kDa subunits that binds to the ends of the GroEL cylinder. GroES gene was amplified by PCR from E.coli and cloned into an expression vector. This protein was overexpressed in E.coli and was purified by using conventional chromatography techniques.

GrpE , co-chaperone of E.coli, participates actively in the response to hyperosomotic and heat shock by preventing the aggregation of stress-denatured proteins in association with DnaK. This protein is the nucleotide exchange factor for DnaK and may function as a thermosensor. Several rounds of ATP-dependent interactions between DnaJ, DnaK and GrpE are required for fully efficient folding.

DnaJ homolog subfamily B member 8 (DNAJB8) is superior suppressors of aggregation and toxicity of disease-associated polyglutamine proteins.DNAJB8 is a member of the DNAJ/HSP40 family of proteins that regulate chaperone activity. DNAJB8 is (de)acetylated at 2 conserved C-terminal lysines which aren’t involved in substrate binding, but do have a role in suppressing protein aggregation. DNAJB8 has been implicated as a cancer-testis antigen and as a cancer stem-like cell antigen involved in renal cell carcinoma.

STUB1, is a cytoplasmic protein whose amino acid sequence is highly preserved across species. STUB1 interacts with the molecular chaperones Hsc70-Hsp70 and Hsp90 through its TPR domain, whereas its U-box domain contains its E3 ubiquitin ligase activity. STUB1 interaction with these molecular chaperones lead to in client substrate ubiquitylation and degradation by the proteasome. therefore, STUB1 acts to tilt the folding-refolding mechanism towards the degradative pathway, and it serves as a link between the two. STUB1 inhibits anchorage-independent cell growth and metastatic potential by degrading oncogenic proteins including SRC-3. Inhibition of tyrosine kinase activity of Her-2/neu by quercetin specifies an lateration in the Her-2/neu structure which promotes STUB1 recruitments and down-regulation of Her-2/neu. STUB1 recognizes and mediates degradation of toxic, oligomeric forms of alphaSyn.

DNAJC15 which is expressed ubiquitously and located on the membrane contains 1 J domain. In many advanced cases of ovarian adenocarcinoma DNAJC15 is absent or down-regulated, due to hypermethylation and allelic loss. Loss of expression correlates with increased resistance to antineoplastic drugs, such as cisplatin. DNAJC15is a crucial component of the TIM23 translocase complex and stimulates the ATPase activity of HSPA9.

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.

DNAJB11 is a member of the evolutionarily conserved DNAJ/HSP40 family of proteins, which regulate molecular chaperone activity by stimulating ATPase activity. DNAJB11 serves as a co-chaperone for HSPA5 and binds directly to both unfolded proteins which are substrates for ERAD and nascent unfolded peptide chains, but dissociates from the HSPA5-unfolded protein complex before folding is completed.

ST13 is an adaptor protein (co-chaperone) that mediates the association of HSP70 & HSP90 and appears in early receptor complexes. ST13 plays a role in the assembly process of glucocorticoid receptor, which requires the assistance of multiple molecular chaperones. The expression of ST13 is downregulated in colorectal carcinoma tissue signifying that is candidate tumor suppressor gene. Through common binding to both Hsp70 and Hsp90, ST13 functions as an adaptor that can integrate Hsp70 and Hsp90 interactions. The expression of ST13 decreases in colorectal cancer tissue compared with that in adjacent normal tissue. ST13 is mostly expressed in colorectal epithelia and adenocarcinoma cells. ST13 functions to promote the efficiency of glucocorticoid receptor maturation in cells. The expression levels of the ST13 gene were significantly decreased in primary tumors compared with adjacent mucosa.

DnaJ homolog subfamily C member 24 (DNAJC24) belongs to the ZCSL family of proteins and each contain one DPH-type zinc finger. DNAJC24 is involved in the synthesis of diphthamide, a protein found on translation elongation factor EF-2 which is the target of bacterial ADP-ribosylating toxins. DNAJC24 stimulates the ATPase activity of few Hsp70-type chaperones. DNAJC24 detected in heart, brain, spleen, lung, liver, kidney and testis.

DnaJ (Hsp40) Homolog, Subfamily B, Member 4 (DNAJB4) is a member of the evolutionarily conserved DNAJ/HSP40 protein family. DNAJB4 subunit configuration is homodimer. DNAJB4 possibly functions as a chaperone. DNAJB4 C-terminal section interacts with the C-terminal tail of OPRM1. DNAJB4 also has an interaction with SDIM1. DNAJB4 is expressed in the heart, pancreas and skeletal muscle, and to a lesser extent in the brain, placenta and liver.