Dual Localized AtHscB Involved in Iron Sulfur Protein Biogenesis in Arabidopsis

Xiang Ming Xu,Simon Geir Møller,Maita Latijnhouwers,Hong Lin,Edward Newbigin

doi:10.1371/journal.pone.0007662

Abstract

BackgroundIron-sulfur clusters are ubiquitous structures which act as prosthetic groups for numerous proteins involved in several fundamental biological processes including respiration and photosynthesis. Although simple in structure both the assembly and insertion of clusters into apoproteins requires complex biochemical pathways involving a diverse set of proteins. In yeast, the J-type chaperone Jac1 plays a key role in the biogenesis of iron sulfur clusters in mitochondria.Methodology/Principal FindingsIn this study we demonstrate that AtHscB from Arabidopsis can rescue the Jac1 yeast knockout mutant suggesting a role for AtHscB in iron sulfur protein biogenesis in plants. In contrast to mitochondrial Jac1, AtHscB localizes to both mitochondria and the cytosol. AtHscB interacts with AtIscU1, an Isu-like scaffold protein involved in iron-sulfur cluster biogenesis, and through this interaction AtIscU1 is most probably retained in the cytosol. The chaperone AtHscA can functionally complement the yeast Ssq1knockout mutant and its ATPase activity is enhanced by AtHscB and AtIscU1. Interestingly, AtHscA is also localized in both mitochondria and the cytosol. Furthermore, AtHscB is highly expressed in anthers and trichomes and an AtHscB T-DNA insertion mutant shows reduced seed set, a waxless phenotype and inappropriate trichome development as well as dramatically reduced activities of the iron-sulfur enzymes aconitase and succinate dehydrogenase.ConclusionsOur data suggest that AtHscB together with AtHscA and AtIscU1 plays an important role in the biogenesis of iron-sulfur proteins in both mitochondria and the cytosol.

Highlights

Iron-sulfur clusters ([Fe–S]) are important prosthetic groups of iron-sulfur proteins involved in numerous vital biological processes, such as respiration, photosynthesis and nitrogen fixation, and inappropriate cluster formation has detrimental consequences in both prokaryotes and eukaryotes [1]
Our data suggest that AtHscB together with AtHscA and AtIscU1 plays an important role in the biogenesis of iron-sulfur proteins in both mitochondria and the cytosol
SufA-like and Nfulike components and monothiol glutaredoxins are proposed to act as scaffold proteins for [Fe-S] biosynthesis [21,30,31,32,33,34] whilst SufSand SufE-like components act as a cysteins desulfurase complex [20,23,24,27,28,38] extracting sulfur from the amino acid cysteine

Summary

Introduction

Iron-sulfur clusters ([Fe–S]) are important prosthetic groups of iron-sulfur proteins involved in numerous vital biological processes, such as respiration, photosynthesis and nitrogen fixation, and inappropriate cluster formation has detrimental consequences in both prokaryotes and eukaryotes [1]. Simple in structure, [Fe–S] are not formed de novo but require an intricate interplay of highly specialized proteins and both genetic and biochemical studies have identified several pathways for the biogenesis and maturation of [Fe-S] in bacteria, yeast and humans [2,3,4,5,6,7,8,9,10,11,12,13,14,15]. Iron-sulfur clusters are ubiquitous structures which act as prosthetic groups for numerous proteins involved in several fundamental biological processes including respiration and photosynthesis. Simple in structure both the assembly and insertion of clusters into apoproteins requires complex biochemical pathways involving a diverse set of proteins. The J-type chaperone Jac plays a key role in the biogenesis of iron sulfur clusters in mitochondria

Methods

Results

Discussion

Conclusion