Presequences conformation

Larsen et al. reported the enzymatic cleavage of a desB30 insuhn B-chain from a presequence (Lys(Boc))6. This spacer shifts the conformation of the growing peptide chain from a y9-structure to a random coil conformation and reduces pep-tide-chain aggregation, which otherwise causes serious synthetic problems. Nova-syn KA [18] was employed as a solid support, but unfortunately, no information about the enzyme used was reported [19]. 

This was the first complete structure of the bc complex. The structure provided information about all 11 subunits and revealed that subunit 9, the mitochondrial targeting presequence of ISP, exists between two core subunits, which are most likely a mitochondrial targeting presequence peptidase. We have solved the structures of the bc complex in two different crystal forms. Surprisingly, the conformation of the Rieske FeS protein was totally different between two crystal forms, and this provided a crucial insight of the electron bifurcation mechanism at the Qp site (see Section II,F). 

Several additional lines of evidence indicate that presequence function is governed by conformational properties of the precursor. The target peptide of yeast mitochondrial cytochrome oxidase subunit IV (COX), fused to murine dihydrofolate reductase (DHFR, a cytoplasmic enzyme). 

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