Efforts have been made to solubilize cytochrome components from particulate fractions of etiolated mung bean seedlings. Low temperature spectrophotometry reveals that the cytochrome composition of mitochondria isolated from whole seedlings is the same as that reported by Bonner for mung bean hypocotyls. On the basis of the identity in position of the alpha-bands in low temperature difference spectra for mitochondria, for a partially purified haemoprotein from mitochondria, and for purified cytochrome b-555, it is suggested that cytochrome b-555 is an intrinsic component of mung bean mitochondria. Difference spectra show that both the mitochondrial and microsomal fractions contain at least 2 b-type cytochromes. Cytochrome b-555 is almost certainly present in the microsomes, since the low temperature difference spectrum for the cytochrome is identical with the spectrum for this particulate fraction.By freezing and thawing mung bean mitochondria in 4% cholate and centrifuging, cytochrome oxidase activity can be concentrated in the supernatant fraction, although it is not completely solubilized. The oxidase is inhibited by high concentrations of cytochrome c. A particle-bound cytochrome c can be obtained from mitochondria by digestion with snake venom. However, the autoxidizability of the preparation indicates that the cytochrome has been solubilized in a modified form. A CO-binding pigment can be obtained from mung bean microsomes by digestion with snake venom.

Journal Article↗

PubMedDate not supplied

Tetranactin, a macrotetrolide antibiotic, suppresses in vitro proliferation of human lymphocytes and generation of cytotoxicity.

Tetranactin, a hydrophobic cyclic antibiotic produced by Streptomyces aureus, has previously been shown to suppress in vitro activation of rat lymphocytes by concanavalin A as well as the onset of experimental autoimmune uveoretinitis in Lewis rats. Here we report the effects of tetranactin on human T and NK lymphocytes in vitro. Tetranactin, at concentrations up to 100 ng/ml, was not toxic to human lymphocytes but completely abrogated the proliferation of human T lymphocytes in response to allogeneic cells in mixed lymphocyte cultures. Tetranactin also blocked the initiation of proliferation in response to interleukin-2, but did not block proliferation of interleukin-2-activated cells. Tetranactin also blocked generation of cytotoxic T lymphocytes and activated killer cells in the mixed lymphocyte culture. However, up to 100 ng/ml tetranactin did not alter the lytic activity of cytotoxic T or NK lymphocytes generated in its absence. The ability of low doses of tetranactin to block the induction of lymphoproliferation is similar to the action of cyclosporin A. Since cyclosporin A is also a cyclic hydrophobic molecule, the immunosuppressive actions of these two agents may involve a similar mechanism.

Adult↗