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M R Boocock

Publications and source records attributed to M R Boocock.

26 records · Page 2Linked to original sources
PubMed1989

Site-specific recombination by Tn3 resolvase: topological changes in the forward and reverse reactions.

Site-specific recombination catalyzed by Tn3 resolvase proceeds with a linkage change, delta Lk, of +4 in the forward resolution reaction and -4 in the catenane fusion reverse reaction. The reverse reaction occurs only at low superhelical densities and gives unknotted circular products, consistent with plectonemic and not solenoidal wrapping of the two recombination sites. The strand exchange topologies are consistent with a mechanism in which resolvase cleaves all four DNA strands and religates them after a 180 degrees rotation of two duplex partners in a right-handed sense for the "forward" reaction, and in a left-handed sense for the "reverse" action. This could be achieved by a 180 degrees rotation of two resolvase subunits within a tetramer with D2 symmetry; we suggest that a different symmetry applies to phage lamda integrase catalysis.

Chloroquine↗
PubMed1989

Site-specific recombination by Tn3 resolvase.

Site-specific recombination processes in microbes bring about precise DNA rearrangements which have diverse and important biological functions. The sites and recombinase enzymes used for these processes fall into two distinct families. Here we describe how experiments with one family, exemplified by the resolution system of transposon Tn3, have provided insight into the ways in which DNA and protein interact to bring together distant recombination sites and promote strand exchange.

Crossing Over, Genetic↗
PubMed1985

The 3-dehydroquinate synthase activity of the pentafunctional arom enzyme complex of Neurospora crassa is Zn2+-dependent.

We have demonstrated the co-purification in constant ratio of all five activities of the pentafunctional arom enzyme complex from Neurospora crassa. Progressive inactivation of the 3-dehydroquinate synthase component of the purified enzyme complex by chelating agents was blocked by the substrate, 3-deoxy-D-arabino-heptulosonate 7-phosphate, but not by the cofactor NAD+. Full activity was restored at Zn2+ concentrations as low as 0.05 nM. Atomic absorption data indicated that the intact enzyme complex contained 1 atom per subunit of tightly bound zinc. The arom 3-dehydroquinate synthase had a calculated turnover number of 19s-1, this being within the narrow range of values obtained for the other four activities of the intact multifunctional enzyme. The Km for 3-deoxy-D-arabino-heptulosonate 7-phosphate was 1.4 microM in a phosphate-free buffer; inorganic phosphate was a competitive inhibitor with respect to 3-deoxy-D-arabino-heptulosonate 7-phosphate.

Alcohol Oxidoreductases↗
PubMed1983

Kinetics of 5-enolpyruvylshikimate-3-phosphate synthase inhibition by glyphosate.

The herbicide glyphosate (N-phosphonomethyl glycine) is a potent reversible inhibitor of the 5-enolpyruvylshikimate-3-phosphate (EPSP) synthase activity of the purified arom multienzyme complex from Neurospora crassa. Inhibition of the EPSP synthase reaction by glyphosate is competitive with respect to phosphoenolpyruvate, with K(i) 1.1 microM, and uncompetitive with respect to shikimate-3-phosphate. The kinetic patterns are consistent with a compulsory order sequential mechanism in which either PEP or glyphosate can bind to an enzyme: shikimate-3-phosphate complex.

3-Phosphoshikimate 1-Carboxyvinyltransferase↗