The mitochondrial proteins AtHscB and AtIsu1 involved in Fe-S cluster assembly interact with the Hsp70-type chaperon AtHscA2 and modulate its catalytic activity.

Mitochondrion

PubMedID: 25462017

Leaden L, Busi MV, Gomez-Casati DF. The mitochondrial proteins AtHscB and AtIsu1 involved in Fe-S cluster assembly interact with the Hsp70-type chaperon AtHscA2 and modulate its catalytic activity. Mitochondrion. 2014;.
Arabidopsis plants contain two genes coding for mitochondrial Hsp70-type chaperon-like proteins, AtHscA1 (At4g37910) and AtHscA2 (At5g09590). Both genes are homologues of the Ssq1 gene involved in Fe-S cluster assembly in yeast. Protein-protein interaction studies showed that AtHscA2 interacts with AtIsu1 and AtHscB, two Arabidopsis homologues of the Isu1 protein and the Jac1 yeast co-chaperone. Moreover, this interaction could modulate the activity of AtHscA2. In the presence of a 1:5:5 molar ratio of AtHscA2:AtIsu1:AtHscB we observed an increase in the Vmax and a decrease in the S0.5 for ATP of AtHscA2. Furthermore, an increase of about 28 - fold in the catalytic efficiency of AtHscA2 was also observed. Results suggest that AtHscA2 in cooperation with AtIsu1 and AtHscB play an important role in the regulation of the Fe-S assembly pathway in plant mitochondria.