caa a22 4500 605507104 CHVBK 20210128100630.0 cr unu---uuuuu 210128e20150901xx s 000 0 eng 10.1007/s00775-015-1285-z doi (NATIONALLICENCE)springer-10.1007/s00775-015-1285-z Functional implications of the interaction between HscB and IscU in the biosynthesis of FeS clusters [Elektronische Daten] [Stefania Iametti, Alberto Barbiroli, Francesco Bonomi] In bacteria, HscB is the cochaperone of HscA in modulating the transfer of 2Fe2S clusters from a cluster-loaded form of the scaffold protein IscU to acceptor apoproteins. HscB binding to the IscU apoform (apoIscU) reportedly impairs the structural flexibility of apoIscU, but the effects of HscB on cluster formation on IscU have never been assessed. We report that presence of HscB impaired the rate—but not the equilibrium—of the appearance of the distinctive circular dichroism signals associated with formation of a stable 2Fe-2S cluster on IscU in reconstitution experiments. This impairment: (1) was independent of the source of cluster sulfide; (2) was not observed for HscB mutants unable to bind IscU; (3) implied formation of a 1/1 HscB/IscU complex; (4) was not observed for a D39A mutant of IscU, with a much more rigid structure than wt IscU. The cluster species assembled on IscU in the presence of HscB were transferred to apoferredoxin at a slower rate than those formed in the absence of HscB, unless ATP and HscA were also present. At contrast, HscB was found to improve the "catalytic” function of IscU with respect to cluster assembly in the presence of a large apoferredoxin excess. Thus, the HscB/IscU interaction may modulate formation and transfer of FeS clusters by accelerating cluster biosynthesis when appropriate target apoproteins are abundant or by slowing it down when the rate of apoprotein synthesis is slow, and cluster-loaded IscU is more likely to play a role as a "FeS storage” protein. Graphical Abstract: SBIC, 2015 Iron-sulfur cluster biosynthesis nationallicence Molecular chaperones nationallicence Scaffold proteins nationallicence Protein-protein interactions nationallicence CD : Circular dichroism nationallicence TD buffer : 0.1M Tris-HCl, pH 8.0, 5mM dithiothreitol nationallicence TDMK buffer : 0.1M Tris-HCl, pH 8.0, 5mM dithiothreitol, 10mM MgCl2, 150mM KCl nationallicence Iametti Stefania Section of Chemical and Biomolecular Sciences, DeFENS, University of Milan, Via Celoria 2, 20133, Milan, Italy aut Barbiroli Alberto Section of Chemical and Biomolecular Sciences, DeFENS, University of Milan, Via Celoria 2, 20133, Milan, Italy aut Bonomi Francesco Section of Chemical and Biomolecular Sciences, DeFENS, University of Milan, Via Celoria 2, 20133, Milan, Italy aut JBIC Journal of Biological Inorganic Chemistry Springer Berlin Heidelberg 20/6(2015-09-01), 1039-1048 0949-8257 20:6<1039 2015 20 775 https://doi.org/10.1007/s00775-015-1285-z text/html Onlinezugriff via DOI BK010053 XK010053 XK010000 Metadata rights reserved Springer special CC-BY-NC licence nationallicence 1 research-article jats NATIONALLICENCE NATIONALLICENCE NL-springer NATIONALLICENCE 856 40 https://doi.org/10.1007/s00775-015-1285-z text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Iametti Stefania Section of Chemical and Biomolecular Sciences, DeFENS, University of Milan, Via Celoria 2, 20133, Milan, Italy aut NATIONALLICENCE 700 1- Barbiroli Alberto Section of Chemical and Biomolecular Sciences, DeFENS, University of Milan, Via Celoria 2, 20133, Milan, Italy aut NATIONALLICENCE 700 1- Bonomi Francesco Section of Chemical and Biomolecular Sciences, DeFENS, University of Milan, Via Celoria 2, 20133, Milan, Italy aut NATIONALLICENCE 773 0- JBIC Journal of Biological Inorganic Chemistry Springer Berlin Heidelberg 20/6(2015-09-01), 1039-1048 0949-8257 20:6<1039 2015 20 775