Waltner M, Weiner H
Department of Biochemistry, Purdue University, West Lafayette, Indiana 47907-1153, USA.
J Biol Chem. 1995 Nov 3;270(44):26311-7. doi: 10.1074/jbc.270.44.26311.
Mitochondrial processing peptidase (MPP) cleaves the signal sequence from a variety of mitochondrial precursor proteins. A subset of mitochondrial proteins, including rhodanese and 3-oxoacyl-CoA thiolase, are imported into the matrix space, yet are not processed. Rhodanese signal peptide and translated protein were recognized by MPP, as both were inhibitors of processing. The signal peptide of precursor aldehyde dehydrogenase consists of a helix-linker-helix motif but when the RGP linker is removed, processing no longer occurs (Thornton, K., Wang, Y., Weiner, H., and Gorenstein, D. G. (1993) J. Biol. Chem. 268, 19906-19914). Disruption of the helical signal sequence of rhodanese by the addition of the RGP linker did not allow cleavage to occur. However, addition of a putative cleavage site allowed the protein to be processed. The same cleavage site was added to 3-oxoacyl-CoA thiolase, but this protein was still not processed. Thiolase and linker-deleted aldehyde dehydrogenase signal peptides were poor inhibitors of MPP. It can be concluded that both a processing site and the structure surrounding this site are important for MPP recognition.
线粒体加工肽酶（MPP）可从多种线粒体前体蛋白上切割信号序列。包括硫氰酸酶和3-氧代酰基辅酶A硫解酶在内的一部分线粒体蛋白被导入线粒体基质空间，但并未被加工。硫氰酸酶信号肽和翻译后的蛋白都被MPP识别，因为它们都是加工过程的抑制剂。前体醛脱氢酶的信号肽由螺旋-连接子-螺旋基序组成，但当RGP连接子被去除后，加工过程就不再发生（桑顿，K.，王，Y.，韦纳，H.，和戈伦斯坦，D.G.（1993年）《生物化学杂志》268卷，19906 - 19914页）。通过添加RGP连接子破坏硫氰酸酶的螺旋信号序列后，切割无法发生。然而，添加一个假定的切割位点后，该蛋白能够被加工。同样的切割位点被添加到3-氧代酰基辅酶A硫解酶上，但该蛋白仍然未被加工。硫解酶和缺失连接子的醛脱氢酶信号肽对MPP的抑制作用较弱。可以得出结论，加工位点及其周围结构对于MPP的识别都很重要。
