Interaction of the iron–sulfur cluster assembly protein IscU with the Hsc66/Hsc20 molecular chaperone system of
            <i>Escherichia</i>
            <i>coli</i>

Hoff, Kevin G.; Silberg, Jonathan J.; Vickery, Larry E.

doi:10.1073/pnas.130201997

Cited by 204 publications

(311 citation statements)

References 42 publications

(29 reference statements)

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“…Hence, in the presence of 150 mM KCl, the basal level ATPase activity of HscA enhanced approximately 100-fold in the presence of a 100-fold excess of both HscB and apo-IscU. Such behavior is typical of Hsp70 chaperones, in general, and similar studies with E. coli Isc proteins reported a 400-fold increase in the ATPase activity of HscA in the presence of HscB and apo-IscU (21).…”

Section: Hsca Atpase Activitymentioning

confidence: 55%

HscA and HscB Stimulate [2Fe-2S] Cluster Transfer from IscU to Apoferredoxin in an ATP-Dependent Reaction

2006

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The role of the Azotobacter vinelandii HscA/HscB co-chaperone system in ISC-mediated iron-sulfur cluster biogenesis has been investigated in vitro by using CD and EPR spectrometry to monitor the effect of HscA, HscB, MgATP, and MgADP on the time course of cluster transfer from [2Fe-2S] IscU to apo-Isc ferredoxin. CD spectra indicate that both HscB and HscA interact with [2Fe-2S] IscU and the rate of cluster transfer was stimulated more than 20-fold in the presence stoichiometric HscA and HscB and excess MgATP. No stimulation was observed in the absence of either HscB or MgATP and cluster transfer was found to be an ATP-dependent reaction based on concomitant phosphate production and the enhanced rates of cluster transfer in the presence of KCl which is known to stimulated HscA ATPase activity. The results demonstrate a role of the ISC HscA/HscB cochaperone system in facilitating efficient [2Fe-2S] cluster transfer from the IscU scaffold protein to acceptor proteins and that [2Fe-2S] cluster transfer from IscU is an ATP-dependent process. The data are consistent with the proposed regulation of the HscA ATPase cycle by HscB and IscU (Silberg, J. J., Tapley, T. L., Hoff, K. G., and Vickery, L. E. (2004) J. Biol. Chem. 279,[53924][53925][53926][53927][53928][53929][53930][53931], and mechanistic proposals for coupling of the HscA ATPase cycle with cluster transfer from [2Fe-2S] IscU to apo-IscFdx are discussed.Iron-sulfur cluster biogenesis proteins in bacteria are commonly encoded by a highly conserved isc (iron-sulfur cluster) gene cluster, iscRSUA-hscBA-fdx (1). Moreover, with the exception of the regulatory protein IscR, homologs of each of these proteins have been shown to be involved in Fe-S cluster biogenesis in eukaryotic organisms (2). Extensive biochemical and genetic studies have established well-defined roles for IscS and IscU, but specific roles for the IscA, HscA, HscB and Fdx proteins remain elusive. IscS is a cysteine desulfurase that catalyzes the conversion of cysteine to alanine (3;4) and thereby provides the inorganic sulfur for assembly or [4Fe-4S] clusters on the IscU scaffold protein (5). In vitro studies have shown thatIscA has the ability to function as either an alternative scaffold for IscS-mediated cluster assembly of or [4Fe-4S] clusters (6;7) or as a specific Fe donor for cluster assembly on IscU (8), but the physiologically relevant role has yet to be determined. Likewise, the specific redox role of the Isc [2Fe-2S] 2+,+ Fdx (ferredoxin) in IscS-mediated cluster assembly has yet to be identified, with reduction of S 0 to S 2− , oxidation of Fe 2+ to Fe 3+ in the assembly of [2Fe-2S] 2+ clusters, and reductive coupling of two [2Fe-2S] 2+ clusters on IscU to yield one [4Fe-4S] 2+ cluster as the most likely candidates (5;9).In vivo gene knockout studies have demonstrated that both HscA (heat shock cognate 66-kDa; Hsc66) and HscB (heat shock cognate 20-kDa; Hsc20), and their eukaryotic homologs, Ssq1 and Jac1, have crucial roles in the maturation of Fe-S proteins in both prokary...

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Section: Hsca Atpase Activitymentioning

confidence: 55%

HscA and HscB Stimulate [2Fe-2S] Cluster Transfer from IscU to Apoferredoxin in an ATP-Dependent Reaction

2006

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“…It is known that superoxide destroys [Fe-S] clusters and inactivates enzymes that contain [Fe-S] (Flint et al 1993), so enough supply of [Fe-S] is important for plant to maintain normal redox and nonredox catalysis under stress. In bacterial, J-type co-chaperone binds Hsc66 and stimulates the ATPase activity of Hsc66, then the complex, together with IscU, is involved in [Fe-S] cluster assembly (Kevin et al 2000). The function of the protein has not been reported in high plant yet.…”

Section: Discussionmentioning

confidence: 99%

Proteomics Analysis of Drought Stress-Responsive Proteins in Hippophae rhamnoides L.

Yao

2008

Plant Mol Biol Rep

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Hippophae rhamnoides L. is uniquely capable of growing well under extreme environmental conditions such as water deficit, low temperature, and high altitude. Such tolerance invokes much interest in understanding the biology of this plant species and its utilization potential. In this study, analysis of drought stress-responsive proteins in H. rhamnoides was conducted wherein greenhousegrown seedlings were subjected to drought stress. By using proteomic techniques, proteins, extracted from leaves, were analyzed using two-dimensional electrophoresis and MALDI-TOF MS. Altogether, 55 proteins exhibited changes in abundance under stress. Of these, 13 proteins were identified, including three that disappeared under drought (a putative ABC transporter ATP-binging protein, a heat shock protein HslU, and a hypothetical protein XP-515578), seven that were up-regulated (three large subunits of rubisco, a hypothetical protein DSM3645-23351, a putative acyl-CoA dehydrogenase, a nesprin-2, and a Jtype co-chaperone HSC20), and three that were only detected under drought (a probable nitrogen regulation protein (NtrX), a 4-hydroxyphenylpyruvate dioxygenase, and an unnamed protein product). These proteins may function in β-oxidation pathways in mitochondria, across membranes transport, abnormal protein removal, or prevent protein aggregation arrest, cell division, cytoskeleton stabilization, iron-sulfur cluster assembly, nitrogen metabolism regulation, and antioxidant substance biosynthesis. Four proteins (J-type co-chaperone Hsc20, a putative ABC transporter ATP-binging protein, NtrX, and HslU) were deemed as new discoveries in higher plants, and their functions were predicted either from their conserved domains or homologies to other organisms. These results provide new insights into our understanding of the mechanism of drought tolerance in plants.

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“…Although the exact role of Hsc66 in this process is unknown, the importance of Hsc66 in iron-sulfur cluster assembly may arise from its interactions with the IscU protein (10). IscU is a small, dimeric protein that is capable of forming labile iron-sulfur clusters in vitro and is proposed to serve as a template for iron-sulfur cluster formation in vivo (10 -12).…”

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confidence: 99%

Contributions of the LPPVK Motif of the Iron-Sulfur Template Protein IscU to Interactions with the Hsc66-Hsc20 Chaperone System

Hoff¹,

Cupp‐Vickery

Vickery

2003

Journal of Biological Chemistry

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Interaction of the iron–sulfur cluster assembly protein IscU with the Hsc66/Hsc20 molecular chaperone system of Escherichia coli

Cited by 204 publications

References 42 publications

HscA and HscB Stimulate [2Fe-2S] Cluster Transfer from IscU to Apoferredoxin in an ATP-Dependent Reaction

HscA and HscB Stimulate [2Fe-2S] Cluster Transfer from IscU to Apoferredoxin in an ATP-Dependent Reaction

Proteomics Analysis of Drought Stress-Responsive Proteins in Hippophae rhamnoides L.

Contributions of the LPPVK Motif of the Iron-Sulfur Template Protein IscU to Interactions with the Hsc66-Hsc20 Chaperone System

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