THE HINGE PROTEIN OF CYTOCHROME-C REDUCTASE FROM POTATO LACKS THE ACIDIC DOMAIN AND HAS NO CLEAVABLE PRESEQUENCE

The 'Hinge' protein of cytochrome c reductase from fungi and mammals i s thought to support electron transport from cytochrome c, to cytochro me c and was reported to be one of the most acidic proteins known. Iso lation and analysis of cDNA clones of the first 'Hinge' protein from a plant source reveals that it has a surplus of basic residues in potat o. While the overall identity between the deduced amino acid sequence of the potato 'Hinge' protein and the proteins from yeast and bovine i s in the range of 40%, the characteristic acidic domain is lacking. Th erefore the numerous theories on the function of the mitochondrial 'Hi nge' protein seem not to apply for the protein from potato. Also the a typical acidic presequence of the 'Hinge' protein from fungi and mamma ls is absent as revealed by N-terminal sequencing of the isolated pota to 'Hinge' protein. Functional implications of these results for the ' Hinge' proteins from other organisms are discussed.