Literature summary for 7.4.2.3 extracted from

Zhai, P.; Stanworth, C.; Liu, S.; Silberg, J.J.
The human escort protein Hep binds to the ATPase domain of mitochondrial hsp70 and regulates ATP hydrolysis (2008), J. Biol. Chem., 283, 26098-26106.

Activating Compound

Activating Compound	Comment	Organism	Structure
human escort protein	Hep, stimulates the activity of mtHsp70 49fold, and also 11.5fold the activity of the isolated ATPase domain. Hep binding to full-length mtHsp70 and its isolated ATPase domain is strongest in the absence of nucleotides	Homo sapiens

Cloned(Commentary)

Cloned (Comment)	Organism
expression of mtHsp70 and its isolated ATPase domain, as well as the ATPase fused to the peptide-binding domain of HscA, in Escherichia coli as insoluble proteins	Homo sapiens
HEK-293 cells are transiently transfected with pHep-EGFP, expression of C-terminally His-tagged Hsp70 without its N-terminal mitochondrial targeting sequence in Escherichia coli, the enzyme is insoluble in absence of human escort protein Hep, also as isolated ATPase domain and a chimera having this domain fused to the peptide-binding domain of HscA, a soluble monomeric chaperone	Homo sapiens

Localization

Localization	Comment	Organism	GeneOntology No.	Textmining
mitochondrion	-	Homo sapiens	5739	-

Molecular Weight [Da]

Molecular Weight [Da]	Molecular Weight Maximum [Da]	Comment	Organism
81000	-	1 * 81000, full-length enzyme in absence of ADP	Homo sapiens
86000	-	1 * 86000, full-legth enzyme in presence of ADP, SDS-PAGE	Homo sapiens

Natural Substrates/ Products (Substrates)

Natural Substrates	Organism	Comment (Nat. Sub.)	Natural Products	Comment (Nat. Pro.)	Rev.
ATP + H2O	Homo sapiens	Hsp70 escort proteins are essential for maintaining the function of yeast mitochondrial hsp70 molecular chaperones(mtHsp70)	ADP + phosphate	-	?
ATP + H2O	Homo sapiens	mtHsp70 exhibits limited solubility due to aggregation mediated by its ATPase domain, residues 47-440, but human escort protein Hep directly enhances chaperone solubility through interactions with this domain	ADP + phosphate	-	?
additional information	Homo sapiens	escort proteins regulate the catalytic activity and solubility of their cognate chaperones, and both forms of regulation arise from interactions with the mtHsp70 ATPase domain, residues 47-440	?	-	?

Organism

Organism	UniProt	Comment	Textmining
Homo sapiens	-	-	-

Purification (Commentary)

Purification (Comment)	Organism
recombinant His-tagged full-length enzyme and isolated ATPase domain from Escherichia coli by nickel affinity chromatography, ammonium sulfate fractionation, anion exchange chromatography, and gel filtration	Homo sapiens

Storage Stability

Storage Stability	Organism
mtHsp70 and Hsp70 ATPase domain remain soluble in the absence of Hep and nucleotides when stored in Tris at pH 8.0. In the case of the ATPase domain, the protein remains soluble at concentrations as high as 0.2 mM even when stored for 24 h at room temperature. However, the mtHsp70 ATPase domain could not be stably stored at high concentrations for a similar period of time in buffers having pH values more closely resembling the physiological environment within Escherichia coli where these proteins are overexpressed, unless it is incubated with equimolar Hep	Homo sapiens

Organism

mtHsp70 and Hsp70 ATPase domain remain soluble in the absence of Hep and nucleotides when stored in Tris at pH 8.0. In the case of the ATPase domain, the protein remains soluble at concentrations as high as 0.2 mM even when stored for 24 h at room temperature. However, the mtHsp70 ATPase domain could not be stably stored at high concentrations for a similar period of time in buffers having pH values more closely resembling the physiological environment within Escherichia coli where these proteins are overexpressed, unless it is incubated with equimolar Hep

Homo sapiens

Substrates and Products (Substrate)

Substrates	Comment Substrates	Organism	Products	Comment (Products)	Rev.
ATP + H2O	Hsp70 escort proteins are essential for maintaining the function of yeast mitochondrial hsp70 molecular chaperones(mtHsp70)	Homo sapiens	ADP + phosphate	-	?
ATP + H2O	mtHsp70 exhibits limited solubility due to aggregation mediated by its ATPase domain, residues 47-440, but human escort protein Hep directly enhances chaperone solubility through interactions with this domain	Homo sapiens	ADP + phosphate	-	?
ATP + H2O	human mtHsp70 exhibits limited solubility due to aggregation mediated by its ATPase domain and show that human Hep directly enhances chaperone solubility through interactions with this domain	Homo sapiens	ADP + phosphate	-	?
ATP + H2O	the human escort protein Hep binds to the ATPase domain, residues 47-440, of mitochondrial Hsp70 and regulates ATP hydrolysis	Homo sapiens	ADP + phosphate	-	?
additional information	escort proteins regulate the catalytic activity and solubility of their cognate chaperones, and both forms of regulation arise from interactions with the mtHsp70 ATPase domain, residues 47-440	Homo sapiens	?	-	?

Subunits

Subunits	Comment	Organism
dimer	full-legth enzyme in presence of ADP, SDS-PAGE	Homo sapiens
monomer	1 * 81000, full-length enzyme in absence of ADP	Homo sapiens
monomer	1 * 86000, full-legth enzyme in presence of ADP, SDS-PAGE	Homo sapiens
More	in absence of nucleotides, Hsp70 also forms oligomeric aggregates of high molecular weight	Homo sapiens

Synonyms

Synonyms	Comment	Organism
Hsp70	-	Homo sapiens
mitochondrial hsp70	-	Homo sapiens
mtHSP70	-	Homo sapiens

Temperature Optimum [°C]

Temperature Optimum [°C]	Temperature Optimum Maximum [°C]	Comment	Organism
25	-	assay at	Homo sapiens

Turnover Number [1/s]

Turnover Number Minimum [1/s]	Turnover Number Maximum [1/s]	Substrate	Comment	Organism	Structure
0.00068	-	ATP	pH 7.5, 25°C, full-length mtHsp70 in absence of Hep	Homo sapiens

pH Optimum

pH Optimum Minimum	pH Optimum Maximum	Comment	Organism
7.5	-	assay at	Homo sapiens

Cofactor

Cofactor	Comment	Organism	Structure
ATP	-	Homo sapiens