Polynucleotide phosphorylase from Micrococcus luteus (formerly Micrococcus lysodeikticw) can be converted from a primer-independent form (Form-I) to a primer-dependent form (Form-T) by limited proteolysis with trypsin. The conversion of Form-I to Form-T is accompanied by the breaking of between five and six peptide bonds per molecule of enzyme, and results in the removal of a small portion of t...

Citrate synthase (EC 4.1.3.7) from Escherichia coti is purified to homogeneity. The minimal molecular weight from amino acid analysis is about 62,000. The molecular weight of sodium dodecyl sulfate monomers is 60,000 to 65,000. Results of peptide fingerprinting suggest that the enzyme is composed of only one kind of subunit. The catalytically active protein is a tetramer with a molecular weight...

A method has been described for the isolation and purification of NADPH-cytochrome cZ reductase from light-grown Rhodopseudomonas spheroides. The enzyme is a nonmetalloflavoprotein with flavin adenine dinucleotide as the prosthetic group, and it catalyzes the reduction of R. spheroides cytochrome c2, 2,6dichloroindophenol, and K,Fe(CN), with NADPH as the electron donor. It does not reduce R. sp...

Sulfhydryl reagents affected the binding properties of the translocator domain, NIII, of enzyme IImtl in two ways: (i) the affinity for mannitol was reduced, and (ii) the exchange rate of bound and free mannitol was increased. The effect on the affinity was very much reduced after solubilization of enzyme IImtl in the detergent decylPEG. The effects were caused exclusively by reaction of the su...

The active site cysteine of pig liver thioltransferase was identified as Cys22. The kinetics of the reaction between Cys22 of the reduced enzyme and iodoacetic acid as a function of pH revealed that the active site sulfhydryl group had a pKa of 2.5. Incubation of reduced enzyme with [1-14C]cysteine prevented the inactivation of the enzyme by iodoacetic acid at pH 6.5, and no stable protein-cyst...

A method has been described for the isolation and purification of NADPH-cytochrome cZ reductase from light-grown Rhodopseudomonas spheroides. The enzyme is a nonmetalloflavoprotein with flavin adenine dinucleotide as the prosthetic group, and it catalyzes the reduction of R. spheroides cytochrome c2, 2,6dichloroindophenol, and K,Fe(CN), with NADPH as the electron donor. It does not reduce R. sp...

Under anaerobic conditions the addition of reduced diphosphopyridine nucleotide to stoichiometric amounts of microsomal cytochrome reductase yields reduced flavin and a nucleotideenzyme complex characterized by a 315-rnp absorption peak (2). The properties of the reactive sulfhydryl groups of the enzyme and the evidence for the participation of only one such group in this reaction have been des...

A DNA nicking-closing enzyme has been purified from the nuclei of mouse L cells to 90% homogeneity. The denatured and reduced form of the enzyme has a molecular weight of 68,000 which is in agreement with the molecular weight of the native enzyme as determined by gel filtration and by sucrose sedimentation velocity assuming the protein is globular. Therefore, the active form of the enzyme is a ...

Ribulose-l,5-bisphosphate Carboxylase, Ribulose-l,5-bisphosphate Oxygenase, Enzyme Confor­ mation, Oxygen Effect, Photosynthesis The effect of oxygen on ribulose-l,5-bisphosphate carboxylase-oxygenase from spinach was in­ vestigated. Both activities were deactivated by removal of oxygen and reversibly reactivated by oxygenation of the enzyme solution. The change in enzyme activities was accompa...

The major DNA-synthesizing enzyme present in Pol A(1) (-)Escherichia coli (DNA polymerase II) has been purified to homogeneity as judged by polyacrylamide gel electrophoresis. The enzyme requires all four deoxynucleoside triphosphates, Mg(++), NH(4) (+), and native DNA for maximal activity. The enzyme activity is sensitive to sulfhydryl reagents and is insensitive to anti-DNA polymerase I antis...