Characterization of the roles of A-type proteins in iron-sulfur cluster biogenesis
Randeniya, Sajini Ransara
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The A-type proteins are a class of [Fe-S]-cluster biogenesis proteins which are found in all domains of life. However, the specific function(s) of these A-type proteins within the mitochondrial and bacterial Fe/S-protein biogenesis are still unknown. The ability of Azotobacter vinelandii(Av) IscA and Arabidopsis thaliana(At) SufA1 to bind Fe and [Fe-S]-cluster has been investigated to assess the potential role(s) of A-type proteins in [Fe-S]-cluster biogenesis. Both A-type proteins have been shown to bind one Fe(III) per homodimer with an intermediate-spin (S = 3/2) Fe(III) center that is most likely 5-coordinate with two or three cysteinate ligands. Further, AtSufA1 is shown to bind one [2Fe-2S]2+-cluster with complete cysteinyl ligation. In addition, in vitro UV-visible CD studies of rapid cluster transfer from AtGrxS14 to AtSufA1 yielding a rate constant of 50000 M-1min-1 and >95% completion within 3min indicate that these two classes of proteins work together in cellular [Fe-S]-cluster trafficking.