Components of Cytochrome System and Purification and Some Properties of c-Type Cytochromes of a Denitrifying Bacterium, Pseudomonas stutzeri

Abstract

The cytochrome system of aerobically grown cells of Pseudomonas stutzeri (van Niel strain) has been studied. This bacterium contains cytochrome components c-552 and b-558 and a carbon monoxide-binding pigment(s). Any direct evidence for the presence of α-type cytochromes has not yet been obtained. Total amount of cytochrome components c-552 and b-558 can account for several per cent of the total cellular proteins. Cytochrome b-558 is bound to the cellular membranes, and cytochrome c-552 and carbon monoxide-binding pigment are found in both soluble and particulate fractions obtained on rupture of cells by sonic oscillation followed by centrifugation at 105, 000×g for 1 hr. Cytochrome c-552 (I) and c-552 (II) are isolated from soluble and particulate fractions, respectively, and purified until homogeneous by several criteria. Cytochrome c-552 (II) is crystallized. Physico-chemical properties of cytochrome c-552 (I) are found to be very similar to those of Pseudomonas cytochromes c-551 of P. aeruginosa and P. fluorscens. Cytochrome c-552 (II) is characterized by the low extinction coefficient at its α-band and the molecular weight determined by the Archibald method is twice as high as that of its minimum molecular weight calculated by the content of heme group.