Abstract
Protein products of the suf operon are involved in iron-sulfur metabolism. SufC is an ATPase that can interact with SufB in the absence of nucleotide. We have studied the transient kinetics of the SufC ATPase mechanism using the fluorescent ATP analogue, 2'(3')-O-N-methylanthraniloyl-ATP (mantATP). mantATP initially binds to SufC weakly. A conformational change of the SufC.mantATP complex then occurs followed by the very slow cleavage of mantATP to mantADP and the rapid release of Pi. In the presence of SufB, the cleavage step is accelerated and the release of mantADP is inhibited. Both of these effects promote the formation of a SufC.mantADP complex. In the absence and presence of SufB, mantADP remains more tightly bound to SufC than mantATP. These studies provide a basis for how the SufB and -C proteins interact in the processes involved in regulating iron-sulfur transfer.
Highlights
Protein products of the suf operon are involved in iron-sulfur metabolism
We have studied the transient kinetics of the SufC ATPase mechanism using the fluorescent ATP analogue, 2(3)-O-N-methylanthraniloyl-ATP. mantATP initially binds to SufC weakly
We have shown by sedimentation equilibrium analytical ultracentrifugation [8] that SufC from Thermotoga maritima is monomeric in solution though the monomers of some ATP-binding subunits of ABCtransporters dimerize in the presence of adenosine nucleotides [11]
Summary
Protein products of the suf operon are involved in iron-sulfur metabolism. SufC is an ATPase that can interact with SufB in the absence of nucleotide. In the absence and presence of SufB, mantADP remains more tightly bound to SufC than mantATP. These studies provide a basis for how the SufB and -C proteins interact in the processes involved in regulating iron-sulfur transfer. The sufC gene is found widely in the bacterial kingdom as well as on the plastid genomes of red algae and the nuclear genomes of the malaria parasite [5] and green plants. The suf operon in E. coli has been annotated to specify components of an iron-regulated ABC2-transporter [7], and SufC itself has sequence homology to the nucleotide-binding subunit of ABC-transporters. No potential ABC membrane-spanning subunits have been identified that bind to SufC, which probably rules out this function
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