title: The MitCHAP-60 disease is due to entropic destabilization of the human mitochondrial Hsp60 oligomer.
abstract: The 60-kDa heat shock protein (mHsp60) is a vital cellular complex that mediates the folding of many of the mitochondrial proteins. Its function is executed in cooperation with the co-chaperonin, mHsp10, and requires ATP. Recently, the discovery of a new mHsp60-associated neurodegenerative disorder, MitCHAP-60 disease, has been reported. The disease is caused by a point mutation at position 3 (D3G) of the mature mitochondrial Hsp60 protein, which renders it unable to complement the deletion of the homologous bacterial protein in Escherichia coli (Magen, D., Georgopoulos, C., Bross, P., Ang, D., Segev, Y., Goldsher, D., Nemirovski, A., Shahar, E., Ravid, S., Luder, A., Heno, B., Gershoni-Baruch, R., Skorecki, K., and Mandel, H. (2008) Am. J. Hum. Genet. 83, 30-42). The molecular basis of the MitCHAP-60 disease is still unknown. In this study, we present an in vitro structural and functional analysis of the purified wild-type human mHsp60 and the MitCHAP-60 mutant. We show that the D3G mutation leads to destabilization of the mHsp60 oligomer and causes its disassembly at low protein concentrations. We also show that the mutant protein has impaired protein folding and ATPase activities. An additional mutant that lacks the first three amino acids (N-del), including Asp-3, is similarly impaired in refolding activity. Surprisingly, however, this mutant exhibits profound stabilization of its oligomeric structure. These results suggest that the D3G mutation leads to entropic destabilization of the mHsp60 oligomer, which severely impairs its chaperone function, thereby causing the disease.
authors.affiliation: Department of Biochemistry, George S. Wise Faculty of Life Sciences, Tel Aviv University, 69778 Tel Aviv.
authors.forename: Avital
authors.initials: A
authors.lastname: Parnas
authors.affiliation: Department of Structural Biology, Weizmann Institute of Science, Rehovot 76100.
authors.forename: Michal
authors.initials: M
authors.lastname: Nadler
authors.affiliation: Department of Biochemistry, George S. Wise Faculty of Life Sciences, Tel Aviv University, 69778 Tel Aviv.
authors.forename: Shahar
authors.initials: S
authors.lastname: Nisemblat
authors.affiliation: Department of Structural Biology, Weizmann Institute of Science, Rehovot 76100. Electronic address: amnon.horovitz@weizmann.ac.il.
authors.forename: Amnon
authors.initials: A
authors.lastname: Horovitz
authors.affiliation: Rappaport Faculty of Medicine and Research Institute, Technion-Israel Institute of Technology and Metabolic Disease Unit, Rambam Health Care Campus, Haifa 31096, Israel.
authors.forename: Hanna
authors.initials: H
authors.lastname: Mandel
authors.affiliation: Department of Biochemistry, George S. Wise Faculty of Life Sciences, Tel Aviv University, 69778 Tel Aviv. Electronic address: azema@tauex.tau.ac.il.
authors.forename: Abdussalam
authors.initials: A
authors.lastname: Azem
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D018834:Chaperonin 60 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D019277:Entropy; D006801:Humans; D051379:Mice; D008928:Mitochondria / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D019636:Neurodegenerative Diseases / Q000378:metabolism*; D017354:Point Mutation; D017510:Protein Folding; D020836:Protein Structure, Quaternary
chemical_list: D018834:Chaperonin 60; D024101:Mitochondrial Proteins
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