The unfolding of cytoplasmic aspartate aminotransferase from pig heart in solutions of guanidinium chloride (GdnHCl) was studied. Data from protein fluorescence, c.d. and thiol-group reactivity indicated that the enzyme was unfolded in 6 M-GdnHCl. Spectroscopic studies showed that this unfolding was accompanied by dissociation of the pyridoxal 5'-phosphate cofactor. On dilution of the GdnHCl, r...

Phleomycin induces DNA breakage in vitro in the presence of the sulphydryl compound dithiothreitol. The reaction appears to be free radical-mediated, and requires oxygen and metal ions. Reaction rate is limited by the concentration of oxygen, which is converted to hydrogen peroxide during DNA breakage. However there is no net change in the sulphydryl compound. The proposed reaction mechanism in...

Several dithiols have been prepared that are useful for the reduction of disuffides in aqueous eolution. The reduction potentid of these dithiols have been determined from the measurement of the equilibriun constant of thiol/disulfide interchange with oxidized dithiothreitol using a tH NMR assay. The values of pK" of some of the dithiols were measured to estimate their rate of reduction of disu...

Adenylate and guanylate cyclases were assayed in silkmoth fat body homogenates by measuring the conversion of [cc-3tP]nucleoside triphosphates to cyclic [32P]nucleotides. Adenylate cyclase was dependent on dithiothreitol, required either Mg2’ or MI?+ for activity, was activated by NaF, and inhibited by Triton X-100. Guanylate cyclase was not dependent on dithiothreitol, was strictly dependent u...

The translocation mode of preprolactin (pPL) across mammalian endoplasmic reticulum was reinvestigated in light of recent findings that nascent secretory polypeptides synthesized in the presence of a highly reducing environment could be translocated posttranslationally and independently of their attachment to the ribosome (Maher, P. A., and S. J. Singer, 1986, Proc. Natl. Acad. Sci. USA, 83:900...

When intact pea (Pisum sativum L.) plants are illuminated, the glycolytic enzyme phosphofructokinase is inactivated. In crude extracts the enzyme is inhibited by dithiothreitol. It would seem that this cytoplasmic enzyme, like glucose-6-P dehydrogenase, is light-inactivated when the enzymes of photosynthetic carbon metabolism are light-activated.