Reversal of the orientation of an integral protein of the mitochondrial outer membrane

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Science  26 Jun 1992:
Vol. 256, Issue 5065, pp. 1815-1817
DOI: 10.1126/science.1615327


The NH2-terminus of the signal-anchor sequence of an integral, bitopic protein of the outer mitochondrial membrane was extended both in amino acid length (from 11 to 38 amino acids) and net charge (from +4 to +8)--changes that confer on the NH2-terminus characteristics of a strong matrix-targeting signal. The protein was inserted into the outer membrane but in an inverted orientation (Ncyto-Cin). These findings suggest that, in common with other membrane systems, the orientation of a protein in the outer mitochondrial membrane can be determined by a signal that causes retention of the NH2-terminus on the cytosolic side of the membrane.