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The aromatic domain 66 YWYWW 70 of subunit VIII of the yeast ubiquinol‐cytochrome c oxidoreductase is important for both assembly and activity of the enzyme
Author(s) -
Lobo-Hajdu Gisele,
van Gaalen Monique,
Grivell Leslie A,
Berden Jan A
Publication year - 1996
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(96)01040-x
Subject(s) - protein subunit , ubiquinol , oxidoreductase , mutant , chemistry , stereochemistry , cysteine , saccharomyces cerevisiae , biochemistry , yeast , coenzyme q – cytochrome c reductase , enzyme , cytochrome c , gene , mitochondrion
The aromatic character of the region 66 YWYWW 70 of the 11‐kDa subunit VIII of ubiquinol‐cytochrome c oxidoreductase ( bc 1 complex) of the yeast Saccharomyces cerevisiae has previously been demonstrated to be important for assembly of a functional complex [Hemrika et al. (1994) FEBS Lett. 344, 15–19]. Especially the aromatic nature of residue 66 appeared to be relevant, as the very low level (5%) of bc 1 complex in the mutant 66 SASAA 70 was restored to nearly 70% of the wild‐type level in a phenotypic revertant with the sequence 66 FASAA 70 . In the present study, three other site‐directed mutants ( 66 SAYAA 70 , 66 SASAW 70 and 66 SWYWW 70 ) were constructed and analysed. The data indicate that the presence of one aromatic residue is enough for a substantial level of assembly and that its position modulates the level of both assembly and electron transfer activity. The results also confirm the relevance of this region of subunit VIII for the formation of the Q out reaction domain, as reported by Hemrika et al. [(1993) Eur. J. Biochem. 215, 601–609]. It is further shown that the lowered specific activity of the mutant described by these authors is not due to the introduction of a cysteine in the sequence of subunit VIII.