title: Characterization of Mutants of Human Small Heat Shock Protein HspB1 Carrying Replacements in the N-Terminal Domain and Associated with Hereditary Motor Neuron Diseases.
abstract: Physico-chemical properties of the mutations G34R, P39L and E41K in the N-terminal domain of human heat shock protein B1 (HspB1), which have been associated with hereditary motor neuron neuropathy, were analyzed. Heat-induced aggregation of all mutants started at lower temperatures than for the wild type protein. All mutations decreased susceptibility of the N- and C-terminal parts of HspB1 to chymotrypsinolysis. All mutants formed stable homooligomers with a slightly larger apparent molecular weight compared to the wild type protein. All mutations analyzed decreased or completely prevented phosphorylation-induced dissociation of HspB1 oligomers. When mixed with HspB6 and heated, all mutants yielded heterooligomers with apparent molecular weights close to ~400 kDa. Finally, the three HspB1 mutants possessed lower chaperone-like activity towards model substrates (lysozyme, malate dehydrogenase and insulin) compared to the wild type protein, conversely the environmental probe bis-ANS yielded higher fluorescence with the mutants than with the wild type protein. Thus, in vitro the analyzed N-terminal mutations increase stability of large HspB1 homooligomers, prevent their phosphorylation-dependent dissociation, modulate their interaction with HspB6 and decrease their chaperoning capacity, preventing normal functioning of HspB1.
authors.affiliation: Department of Biochemistry, School of Biology, Moscow State University, Moscow 119991, Russian Federation.
authors.forename: Lydia K
authors.initials: LK
authors.lastname: Muranova
authors.affiliation: Laboratory for Biocrystallography, Department of Pharmaceutical and Pharmacological Sciences, KU Leuven, 3000 Leuven, Belgium.
authors.forename: Stephen D
authors.initials: SD
authors.lastname: Weeks
authors.affiliation: Laboratory for Biocrystallography, Department of Pharmaceutical and Pharmacological Sciences, KU Leuven, 3000 Leuven, Belgium.
authors.forename: Sergei V
authors.initials: SV
authors.lastname: Strelkov
authors.affiliation: Department of Biochemistry, School of Biology, Moscow State University, Moscow 119991, Russian Federation.
authors.forename: Nikolai B
authors.initials: NB
authors.lastname: Gusev
mesh_terms: D050886:HSP20 Heat-Shock Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D055551:HSP27 Heat-Shock Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D006360:Heat-Shock Proteins; D006801:Humans; D018832:Molecular Chaperones / Q000737:chemistry / Q000235:genetics; D009046:Motor Neurons / Q000378:metabolism* / Q000473:pathology; D009134:Muscular Atrophy, Spinal / Q000188:drug therapy / Q000235:genetics* / Q000473:pathology; D009154:Mutation; D010766:Phosphorylation; D066263:Protein Aggregation, Pathological / Q000235:genetics; D011485:Protein Binding / Q000235:genetics; D055503:Protein Multimerization / Q000235:genetics; D020836:Protein Structure, Quaternary; D059748:Proteolysis
chemical_list: D050886:HSP20 Heat-Shock Proteins; D055551:HSP27 Heat-Shock Proteins; C057725:HSPB1 protein, human; C494382:HSPB6 protein, human; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones