SufA/IscA: reactivity studies of a class of scaffold proteins involved in [Fe-S] cluster assembly.
IscA/SufA proteins belong to complex protein machineries which are involved in iron-sulfur cluster biosynthesis. They are defined as scaffold proteins from which preassembled clusters are transferred to target apoproteins. The experiments described here demonstrate that the transfer reaction proceeds in two observable steps: a first fast one leading to a protein-protein complex between the cluster donor (SufA/IscA) and the acceptor (biotin synthase), and a slow one consisting of cluster transfer leading to the apoform of the scaffold protein and the holoform of the target protein. Mutation of cysteines in the acceptor protein specifically inhibits the second step of the reaction, showing that these cysteines are involved in the cluster transfer mechanism but not in complex formation. No cluster transfer from IscA to IscU, another scaffold of the isc operon, could be observed, whereas IscU was shown to be an efficient cluster source for cluster assembly in IscA. Implications of these results are discussed.
Laboratoire de Chimie et Biochimie des Centres Rédox Biologiques, DRDC-CB, CEA/CNRS/Université Joseph Fourier, UMR 5047, 17 Avenue des Martyrs, 38054 Grenoble Cedex 09, France.
S
S
Ollagnier-de-Choudens
Y
Y
Sanakis
M
M
Fontecave
D001059:Apoproteins / Q000737:chemistry / Q000378:metabolism; D002352:Carrier Proteins / Q000737:chemistry* / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism; D007501:Iron / Q000737:chemistry*; D007506:Iron-Sulfur Proteins / Q000737:chemistry* / Q000378:metabolism; D013057:Spectrum Analysis; D013455:Sulfur / Q000737:chemistry*; D013466:Sulfurtransferases / Q000737:chemistry / Q000378:metabolism; D013997:Time Factors
D001059:Apoproteins; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D007506:Iron-Sulfur Proteins; C487901:IscA protein, E coli; C499169:SufA protein, E coli; D013455:Sulfur; D007501:Iron; D013466:Sulfurtransferases; C057985:biotin synthetase