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Although the genes of the aceBAK operon are expressed from the same promoter, the relative cellular levels of their products are approximately 0.3:1:0.003. Gene and operon fusions with lacZ were constructed to characterize this differential expression. The upshift in expression between aceB and aceA resulted from differences in translational efficiency. In(More)
Interactions between calmodulin (CaM) and several hydrophobic fluorescent probes were characterized in order to determine if CaM expresses hydrophobic binding sites in the presence of Ca2+. Several classes of fluorescent probes capable of sensing exposure of hydrophobic binding sites on proteins were found to bind to CaM, and these interactions were greatly(More)
The control of the glyoxylate bypass operon (aceBAK) of Escherichia coli is mediated by two regulatory proteins, IclMR and FadR. IclMR is a repressor protein which has previously been shown to bind to a site which overlaps the aceBAK promoter. FAR is a repressor/activator protein which participates in control of the genes of fatty acid metabolism. A(More)
In Escherichia coli, the branch point between the Krebs cycle and the glyoxylate bypass is regulated by the phosphorylation of isocitrate dehydrogenase (IDH). Phosphorylation inactivates IDH, forcing isocitrate through the bypass. This bypass is essential for growth on acetate but does not serve a useful function when alternative carbon sources, such as(More)
In the yeast Saccharomyces cerevisiae, glycogen synthase is encoded by two genes: GSY1 and GSY2. The activity of the enzymes increases as cultures enter the stationary phase of growth. Using a GSY2::lacZ fusion gene, we have demonstrated that the increase in glycogen synthase activity resulted, at least in part, from an increase in the level of the protein(More)
The interdependence of the activities of branch point enzymes which compete for a common substrate can yield ultrasensitivity or subsensitivity to control, even if the competing enzymes follow Michaelis-Menten kinetics. The nature of this "branch point effect" for a particular system depends on the kinetic parameters of the competing enzymes, the rate of(More)
Isocitrate dehydrogenase from Bacillus subtilis (BsIDH) is a member of a family of metal-dependent decarboxylating dehydrogenases. Its crystal structure was solved to 1.55 A and detailed comparisons with the homologue from Escherichia coli (EcIDH), the founding member of this family, were made. Although the two IDHs are structurally similar, there are three(More)
In Escherichia coli, repression of the aceBAK operon is mediated by the IclR protein. We used an in vitro oligonucleotide selection technique to determine the consensus recognition sequence for MR. Mutational analysis confirmed the contribution of this sequence to repression in vivo and identified the -35 element of the promoter.
Polymyxin B was attached to agarose beads by stable covalent bonds and the antimicrobial activity of the immobilized peptide was examined. Polymyxin-agarose inhibited the growth of Escherichia coli and Pseudomonas aeruginosa, but not Bacillus subtilis. In addition, the respiration of E. coli, E. coli spheroplasts, and B. subtilis protoplasts was inhibited(More)
Regulation of a wide variety of biological systems by Ca2+ is now known to be mediated through calmodulin, a Ca2+-binding protein. Calmodulin forms Ca2+-dependent complexes with several proteins, including troponin I. We have determined the free-energy coupling (delta GoCT) for binding of Ca2+ and troponin I to calmodulin by measuring Ca2+ binding to(More)