Poster abstracts

Poster number 55 submitted by Stephen Pearson

Fe-S Cluster Synthesis and Transport: Defining the Mechanism of [2Fe-2S](GS)4 Export Through an ABCB7 like Exporter

Stephen A. Pearson (Biophysics), James A Cowan (Chemistry and Biochemistry)

Abstract:
Iron-sulfur (Fe-S) clusters are common cofactors found in essentially all living organisms. In humans, Fe-S clusters are made predominately in the mitochondria, but assembly machinery is also present in the cytosol. However, when mitochondrial Fe-S cluster assembly is inhibited, some cytosolic Fe-S cluster proteins are not able to convert to their holo forms due to lack of cluster.2 One hypothesis is that an Fe-S cluster precursor molecule is transported out of the mitochondria, but we believe this molecule to be the Fe-S cluster itself, coordinated to four glutathione molecules [2Fe-2S](GS)4. The glutathione coordinated cluster has been showed to be stabilized through salt bridges between glutathione molecules. Through liposome transport studies, we have shown that ABC transporter S. cerevisiae Atm1p is able to transport [2Fe-2S](GS)4 clusters. The ATPase activity of Atm1p is stimulated in the presence of both glutathione and [2Fe-2S](GS)4. Michalis-Menton kinetics show that [2Fe-2S](GS)4 lower the Km for Mg-ATP for WT Atm1p, which may lay insight onto the mechanism of cluster export out of the mitochondria.

Keywords: membrane protein, iron-sulfur clusters