The Mammalian Proteins MMS19, MIP18, and ANT2 Are Involved in Cytoplasmic Iron-Sulfur Cluster Protein Assembly

Niek Van Wietmarschen,Annie Moradian,Gregg B Morin,Peter M Lansdorp,Evert-Jan Uringa

doi:10.1074/jbc.m112.431270

Abstract

Iron-sulfur (Fe-S) clusters are essential cofactors of proteins with a wide range of biological functions. A dedicated cytosolic Fe-S cluster assembly (CIA) system is required to assemble Fe-S clusters into cytosolic and nuclear proteins. Here, we show that the mammalian nucleotide excision repair protein homolog MMS19 can simultaneously bind probable cytosolic iron-sulfur protein assembly protein CIAO1 and Fe-S proteins, confirming that MMS19 is a central protein of the CIA machinery that brings Fe-S cluster donor proteins and the receiving apoproteins into proximity. In addition, we show that mitotic spindle-associated MMXD complex subunit MIP18 also interacts with both CIAO1 and Fe-S proteins. Specifically, it binds the Fe-S cluster coordinating regions in Fe-S proteins. Furthermore, we show that ADP/ATP translocase 2 (ANT2) interacts with Fe-S apoproteins and MMS19 in the CIA complex but not with the individual proteins. Together, these results elucidate the composition and interactions within the late CIA complex.

Highlights

MMS19 was recently identified as part of the cytosolic iron-sulfur (Fe-S) cluster assembly (CIA) machinery
We show that MIP18 is capable of binding directly to both CIAO1 and Fe-S proteins and that it binds to the Fe-S cluster coordinating regions of Fe-S target proteins
CIA complex member CIAO1 was repeatedly found as a potential MMS19-interacting protein as well as MMXD (MMS19-MIP18-XPD) complex members MIP18 and ANT2 [13]

Summary

Background

MMS19 was recently identified as part of the cytosolic iron-sulfur (Fe-S) cluster assembly (CIA) machinery. Results: MMS19 and MIP18 both interact with CIA and Fe-S proteins, and ANT2 binds to this complex. We show that ADP/ATP translocase 2 (ANT2) interacts with Fe-S apoproteins and MMS19 in the CIA complex but not with the individual proteins. The Fe-S cluster is subsequently further processed by the cytosolic iron-sulfur cluster assembly (CIA) machinery, after which the clusters are incorporated into their target proteins [2]. Both the ISC and CIA systems are highly conserved in eukaryotes, from yeast to human, pointing to the crucial importance of proper Fe-S cluster assembly [3]. We propose that ANT2 is required to stabilize the interaction between MMS19 and Fe-S proteins

EXPERIMENTAL PROCEDURES

RESULTS

DISCUSSION