title: Ssq1, a mitochondrial Hsp70 involved in iron-sulfur (Fe/S) center biogenesis. Similarities to and differences from its bacterial counterpart.
abstract: The results of in vivo and in organellar experiments indicate that the Hsp70 Ssq1 and the J-protein Jac1 function together to assist in the biogenesis of iron-sulfur (Fe/S) centers in the mitochondrial matrix. Here we present biochemical evidence supporting this idea. Isu, the proposed scaffold on which Fe/S centers are assembled, is a substrate for both Jac1 and Ssq1. Jac1 and Isu1 cooperatively stimulate the ATPase activity of Ssq1. In addition, Jac1 facilitates the interaction of Ssq1 with Isu1 in the presence of ATP. These findings are consistent with the role in Fe/S biogenesis previously proposed for the bacterial Hsp70 Hsc66 and J-protein Hsc20 that interact with the bacterial Isu homologue IscU. However, unlike the bacterial Hsp70, we found that Ssq1 has a high affinity for nucleotide, and shares a nucleotide exchange factor, Mge1, with a second mitochondrial Hsp70, Ssc1. Thus, whereas the bacterial and mitochondrial chaperone systems share critical features, they possess significant biochemical differences as well.
authors.affiliation: Department of Molecular and Cellular Biology, Faculty of Biotechnology, University of Gdansk, 24 Kladki, 80-822 Gdansk, Poland.
authors.forename: Rafal
authors.initials: R
authors.lastname: Dutkiewicz
authors.forename: Brenda
authors.initials: B
authors.lastname: Schilke
authors.forename: Helena
authors.initials: H
authors.lastname: Knieszner
authors.forename: William
authors.initials: W
authors.lastname: Walter
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Craig
authors.forename: Jaroslaw
authors.initials: J
authors.lastname: Marszalek
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D002499:Centrifugation, Density Gradient; D004591:Electrophoresis, Polyacrylamide Gel; D029968:Escherichia coli Proteins; D005990:Glycerol / Q000378:metabolism; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D006360:Heat-Shock Proteins / Q000378:metabolism; D006868:Hydrolysis; D007506:Iron-Sulfur Proteins / Q000378:metabolism*; D007700:Kinetics; D026901:Membrane Transport Proteins / Q000378:metabolism; D033681:Mitochondrial Membrane Transport Proteins; D024101:Mitochondrial Proteins; D018832:Molecular Chaperones / Q000378:metabolism* / Q000502:physiology*; D011485:Protein Binding; D011994:Recombinant Proteins / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism / Q000502:physiology*; D020349:Surface Plasmon Resonance; D013997:Time Factors
chemical_list: D029968:Escherichia coli Proteins; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; C121520:ISU1 protein, S cerevisiae; D007506:Iron-Sulfur Proteins; C115914:JAC1 protein, S cerevisiae; C086039:MGE1 protein, S cerevisiae; D026901:Membrane Transport Proteins; D033681:Mitochondrial Membrane Transport Proteins; D024101:Mitochondrial Proteins; D018832:Molecular Chaperones; D011994:Recombinant Proteins; C115913:SSQ1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C085650:hscA protein, E coli; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases; D005990:Glycerol