In Cellulo Mössbauer and EPR Studies Bring New Evidence to the Long-Standing Debate on Iron-Sulfur Cluster Binding in Human Anamorsin.

Sara Matteucci,Geneviève Blondin,Lucia Banci,Francesca Camponeschi,Martin Clémancey,Simone Ciofi‐Baffoni

doi:10.1002/anie.202102910

Abstract

Human anamorsin is an iron–sulfur (Fe–S)‐cluster‐binding protein acting as an electron donor in the early steps of cytosolic iron–sulfur protein biogenesis. Human anamorsin belongs to the eukaryotic CIAPIN1 protein family and contains two highly conserved cysteine‐rich motifs, each binding an Fe–S cluster. In vitro works by various groups have provided rather controversial results for the type of Fe–S clusters bound to the CIAPIN1 proteins. In order to unravel the knot on this topic, we used an in cellulo approach combining Mössbauer and EPR spectroscopies to characterize the iron–sulfur‐cluster‐bound form of human anamorsin. We found that the protein binds two [2Fe–2S] clusters at both its cysteine‐rich motifs.

Highlights

Human anamorsin is an iron–sulfur (Fe–S)-clusterbinding protein acting as an electron donor in the early steps of cytosolic iron–sulfur protein biogenesis
The hallmark of this protein family is the presence, in the cytokine-induced apoptosis inhibitor 1 (CIAPIN1) domain, of two highly conserved cysteine-rich motifs (a CX8CX2CXC motif (M1 motif, hereafter) followed by a CX2CX7CX2C motif (M2 motif, hereafter)), each able to bind an Fe–S cluster.[6,7,8,9,10]. This protein in human,[11] yeast,[12] plant[13,14,15] and in the protist Trypanosoma brucei[16] has been proposed to act in the early stages of the cytoplasmic Fe–S protein biogenesis by working as an electron donor in an electron transfer chain required for the assembly of [4Fe–4S] clusters
At 70 K, the in cellulo EPR difference spectrum was dominated by the signal arising from the S = 1/2 spin of the [2Fe–2S]+ cluster bound to the M1 motif of WTanamorsin.[7]

Summary

Introduction

Human anamorsin is an iron–sulfur (Fe–S)-clusterbinding protein acting as an electron donor in the early steps of cytosolic iron–sulfur protein biogenesis. The in cellulo EPR difference spectra (obtained as reported in the Supporting Information) of reduced E. coli cells expressing M2-anamorsin exhibited a rhombic spectrum over a wide range of temperatures (Figure 2 A), indicating that the signal arises from spectra of induced cells.

Results

Conclusion