Cytochrome Oxidase from Etiolated Corn Seedlings

Dutch, Rebecca Ellis; Ingle, Robert T.; Centeno, José A.; Peiffer, Wendy E.; Babcock, Gerald T.; Ferguson‐Miller, Shelagh

doi:10.1007/978-1-4899-3517-5_49

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“…Mitochondria prepared by the method of Day and Hanson (1977) from etiolated wheat seedlings had respiratory control ratios ranging from 5.0 to 7.0, although they deteriorated after an hour. ADP/O ratios were 2.7-2.9 using glutamate/malate as substrate, similar to those reported for maize mitochondria (Dutch et al, 1987). In contrast, the respiration rates of mitochondrial membrane fractions from wheat germ were not stimulated by ADP, and exogenously supplied cytochrome c had complete access to cytochrome oxidase, indicating that the mitochondria were not intact.…”

Section: Resultssupporting

confidence: 84%

“…The plant cytochrome c oxidases studied so far, sweet potato (Maeshima & Asahi, 1978;Nakagawa et al, 1987), pea (Matsuoka et al, 1981), and maize (Dutch et al, 1987;Hawkesford et al, 1989), have a subunit composition different from other eukaryotic oxidases, apparently containing only seven or eight peptides. The three mitochondrially encoded subunits of the plant enzyme are similar in sequence and *To whom correspondence should be addressed.…”

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confidence: 99%

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Structurally unique plant cytochrome c oxidase isolated from wheat germ, a rich source of plant mitochondrial enzymes

Peiffer¹,

Ingle²,

Ferguson‐Miller³

1990

Biochemistry

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Purification and characterization of plant cytochrome c oxidases have been impeded by the difficulty of obtaining enough plant mitochondria. We have found commercial wheat germ to be a rich and convenient source of mitochondrial membranes containing respiratory chain complexes in ratios and amounts similar to mitochondria prepared from etiolated seedlings. Cytochrome c oxidase was purified from these membranes by anion-exchange (MonoQ) fast protein liquid chromatography. The enzyme is highly active (turnover number up to 1000 s-1) and exhibits biphasic cytochrome c reaction kinetics similar to those of beef heart oxidase. As with other plant oxidases, the visible spectrum of wheat germ oxidase in the reduced form is blue-shifted compared to other eukaryotic cytochrome oxidases, with peaks at 441 and 602 nm. The electron paramagnetic resonance spectrum of CuA of the wheat germ enzyme is very similar to that of the maize and beef heart enzymes, suggesting that the copper environment is not altered. Sodium dodecyl sulfate-polyacrylamide gels show a subunit composition in which subunits I-IV resemble those of the yeast enzyme in size and antigenicity, while three to four smaller peptides are dissimilar to yeast and other eukaryotic oxidases. A difference between the subunit composition of the wheat germ and wheat seedling enzymes suggests the existence of a developmental or tissue-specific form of cytochrome oxidase in plants.

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Section: Resultssupporting

confidence: 84%

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confidence: 99%