Changes in cytochrome composition of Rhodopseudomonas sphaeroides f. sp. denitrificans grown under denitrifying conditions

Abstract

Electrophoretic and spectrophotometric techniques have been used to detect changes in the cytochrome composition of Rhodopseudomonas sphaeroides f. sp. denitrificans during adaptation to denitrifying conditions. During photosynthetic growth with nitrate, the amounts of soluble cytochrome c were depressed relative to those found in cells grown without nitrate. This effect was associated with a loss of two soluble, CO- and NO-binding cytochromes, namely cytochrome c′ and cytochrome c-551.5. When cells were grown under denitrifying conditions a 21 kDa b-type membrane cytochrome was also not detected, but there was an increase in the amount of another membrane 24 kDa b-type cytochrome. A new high potential (Em, 7 = 252mV) soluble cytochrome, namely cytochrome c-552, was also synthesized under these conditions. The cytochrome composition of either membrane or soluble fractions of Rps. sphaeroides f.sp. denitrificans grown in light without nitrate, was very similar to that of the wild-type (non-denitrifying) Rps. sphaeroides. Show more