Human dUTPase, essential for DNA integrity, is an important survival factor for cancer cells. We determined the crystal structure of the enzyme:a,b-imino-dUTP:Mg complex and performed equilibrium binding experiments in solution.Ordering of the C-terminus upon the active site induces close juxtaposition of the incoming nucleophile attacker water oxygen and the a-phosphorus of the substrate, decreasing their distance below the van der Waals limit. Complex interactions of the C-terminus with both substrate and product were observed via a specifically designed tryptophan sensor, suitable for further detailed kinetic and ligand binding studies. Results explain the key functional role of the C-terminus.
From the pressure induced frequency shift of photochemical holes burnt into mesomorphyrin substituted horseradish peroxidase, we determined the compressibility of the protein and the vacuum frequency of the chromophore. From the compressibility, an estimation of the volume fluctuations of the biomolecule is possible.
We have measured the low-temperature absorption and the depolarization ratio dispersion of various intense resonance Raman lines of horseradish peroxidase C. The absorption spectra reveal significant splitting of the Q and charge-transfer bands whereas the Soret band solely exhibits a narrowing of the band profile. The depolarization ratios of all Raman lines investigated are different from expectation values in D 4h symmetry and show significant dispersion in the preresonance and resonance region of the Q v band. All these data indicate symmetry lowering distortions of the heme macrocycle. An analysis of the depolarization ratios shows that in-plane B 1g -and B 2g -type perturbations distort the heme along the N-Fe-N and C m -Fe-C m line of the heme. The B 1g perturbation gives rise to the band splitting in the optical spectrum and to a rhombicity of the iron's ligand field detected by EPR experiments. On the basis of group theoretical arguments we propose that particularly the strong B 2g distortion gives rise to the quantum mixed spin state characteristic of class III peroxidases.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.