Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.24.64 (MPP)
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Cytochrome-c reductase (EC 1.10.2.2.) from Solanum tuberosum L. comprises ten subunits with apparent molecular sizes of 55, 53, 51, 35, 33, 25, 14, 12, 11 and 10 kDa on 14% SDS-PAGE. The identity of the subunits was analysed by direct amino-acid sequencing via cyclic Edman degradation. A large-scale purification procedure for the enzyme complex based on affinity chromatography and gelfiltraton is described. All subunits were enzymatically fragmented and the generated peptides were separated by reverse-phase HPLC. Complete or partial sequence determination of 33 peptides comprising a total of nearly 500 amino acids showed, that cytochrome-c reductase from potato contains three respiratory proteins (cytochrome b, cytochrome c1, and the "Rieske" iron-sulfur protein), four small proteins with molecular sizes below 15 kDa (so-called Q-binding, hinge, cytochrome-c1-linked and core-linked proteins) and three proteins in the 50-kDa range which show similarity to members of the core/PEP/MPP protein family (core/processing enhancing protein/mitochondrial processing peptidase). In fact these subunits show highest sequence identity either to MPP or PEP, which is in line with earlier findings, that isolated cytochrome-c reductase from potato exhibits processing activity towards mitochondrial precursor proteins.
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PMID:Molecular identification of the ten subunits of cytochrome-c reductase from potato mitochondria. 776 24

The bc1-complex (EC 1.10.2.2.) from Triticum aestivum L. was purified by cytochrome-c affinity chromatography and gel filtration using either etiolated seedlings or wheat-germ extract as starting material. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the isolated enzyme revealed ten bands, which were analysed by immunoblotting and direct amino-acid sequencing. The enzyme from wheat is the first bc1-complex that is reported to contain four core proteins (55.5, 55.0, 51.5 and 51.0 kDa). In addition, the wheat bc1-complex comprises cytochrome b (35 kDa), cytochrome c1 (33 kDa) the "Rieske" iron-sulphur protein (25 kDa) and three small subunits < 15 kDa. This composition differs from the one reported in fungi, mammals and potato. Partial sequence determination of the large subunits suggests that the 55.5- and 55.0-kDa-proteins represent the beta-subunit of the general mitochondrial processing peptidase, and the 51.5- and 51.0-kDa proteins the alpha-subunit of this enzyme. The bc1-complex from wheat efficiently processes mitochondrial precursor proteins as shown in an in-vitro processing assay. In control experiments the isolated bc1-complexes from potato, yeast, Neurospora and beef, all purified by the same isolation procedure, were also tested for processing activity. Only the protein complexes from plants contain the general mitochondrial processing peptidase. The composition of the wheat bc1-complex sheds new light on the co-evolution of the processing peptidase and the middle segment of the respiratory chain.
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PMID:The general mitochondrial processing peptidase from wheat is integrated into the cytochrome bc1-complex of the respiratory chain. 776 45