Membrane-bound redox proteins of the murine Friend virus-induced erythroleukemia cell.

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Abstract
We have obtained and studied a 105,000-g pellet from T-3-C1-2 cells, a cloned line of Friend virus-induced erythroleukemia cells. By difference spectrophotometry, the pellet contained cytochrome b5 and cytochrome P-450, hemeproteins that participated in electron-transport reactions of endoplasmic reticulum and other membranous fractions of various tissues. The pellet also possesses NADH-cytochrome c reductase activity which is inhibited by anti-cytochrome b5 .gamma.-globulin, indicating the presence of cytochrome b5 reductase. This is the first demonstration of membrane-bound forms of these redox proteins in erythroid cells. Dimethyl sulfoxide-treated T-3-C1-2 cells also possessed membrane-bound cytochrome b5 and NADH-cytochrome c reductase activity. Soluble cytochrome b5 in the 105,000-g supernatant fraction from homogenates of untreated or dimethyl sulfoxide-treated T-3-C1-2 cells. Erythrocytes obtained from mouse blood were shown to possess soluble cytochrome b5 but no membrane-bound form of this protein. These findings show that soluble cytochrome b5 of erythrocytes is derived from endoplasmic reticulum or some other membrane structure of immature erythroid cells during cell maturation.