CELL BIOLOGY: Stretched for the Guillotine

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Science  20 Jul 2001:
Vol. 293, Issue 5529, pp. 395c
DOI: 10.1126/science.293.5529.395c

The presence of many membrane-bounded compartments in a eukaryotic cell means that proteins must have signal sequences that target them to the appropriate organelle and that organelles must have translocation machinery to import these proteins. Although the signal sequences appear to adopt an α-helical conformation during translocation, Taylor et al. show that the mitochondrial processing peptidase—a thermolysin-like zinc-dependent protease—recognizes an extended or β strand-like conformation of the signal sequence. The peptidase active site utilizes both position-dependent binding sites for arginine and aromatic side chains as well as main chain interactions with the edge of a β sheet in order to accommodate the wide variety of sequences. — GJC

Structure 9, 615 (2001).

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