On 2014 Oct 26, EDWARD BERRY commented:

The potato hinge protein has a perfect CX9CX3C----CX3CX9C motif which by homology with vertebrate structures should form a helix hairpin with disulfides holding the two arms together. This is the motif recognized by the MIA40/CHCHD4 disulfide relay import system. And like other MIA40 substrates, the hinge protein ends up in the inter-membrane space (attached to cyt c1 of the bc1 complex). I wonder if anyone has checked whether Hinge is imported by the MIA40 system.

In vertebrates one of the middle cysteines is lost, some residues are inserted, spoiling the perfect cannonical MIA40 import sequence. Only two disulfides are formed, and there is a short leader sequence although it is not a typical mitochondrial targeting sequence.

In Saccharomyces, all but two of the cysteines are lost, and the hairpin is clamped by a single disulfide. Could this represent a switch from one import mechanism to another over the course of evolution?

On 2014 Oct 26, EDWARD BERRY commented:

The potato hinge protein has a perfect CX9CX3C----CX3CX9C motif which by homology with vertebrate structures should form a helix hairpin with disulfides holding the two arms together. This is the motif recognized by the MIA40/CHCHD4 disulfide relay import system. And like other MIA40 substrates, the hinge protein ends up in the inter-membrane space (attached to cyt c1 of the bc1 complex). I wonder if anyone has checked whether Hinge is imported by the MIA40 system.

In vertebrates one of the middle cysteines is lost, some residues are inserted, spoiling the perfect cannonical MIA40 import sequence. Only two disulfides are formed, and there is a short leader sequence although it is not a typical mitochondrial targeting sequence.

In Saccharomyces, all but two of the cysteines are lost, and the hairpin is clamped by a single disulfide. Could this represent a switch from one import mechanism to another over the course of evolution?