[Show abstract][Hide abstract] ABSTRACT: DNA photolyase is a unique flavoenzyme that repairs UV-induced DNA lesions using the energy of visible light. Anacystis nidulans photolyase contains a light-harvesting chromophore, 8-hydroxy-5-deazaflavin (8-HDF), and flavin adenine dinucleotide (FAD) which, in contrast to the 8-HDF chromophore, is indispensable for catalytic activity. This work reports the crystallization and structure at 1.8 A resolution of DNA photolyase devoid of its 8-HDF chromophore (apophotolyase). The overall three-dimensional structure is similar to that of the holoenzyme, indicating that the presence of 8-HDF is not essential for the correct folding of the enzyme. Structural changes include an additional phosphate group, a different conformation for Arg11 and slight rearrangements of Met47, Asp101 and Asp382, which replace part of the 8-HDF molecule in the chromophore-binding pocket. The apophotolyase can be efficiently reconstituted with synthetic 8-hydroxy-5-deazariboflavin, despite the orientation of Arg11 and the presence of the phosphate group in the 8-HDF pocket. Red light or X-rays reduced the FAD chromophore in apophotolyase crystals, as observed by single-crystal spectrophotometry. The structural effects of FAD reduction were determined by comparison of three data sets that were successively collected at 100 K, while the degree of reduction was monitored online by changes in the light absorption of the crystals. X-ray-induced conformational changes were confined to the active site of the protein. They include sub-ångström movements of the O(2) and N(5) atoms of the flavin group as well as the O(delta) atoms of the surrounding amino acids Asp380 and Asn386.
Full-text · Article · Aug 2004 · Acta Crystallographica Section D Biological Crystallography
[Show abstract][Hide abstract] ABSTRACT: The carbon monoxide complex of [NiFe]hydrogenase from Desulfovibrio vulgaris Miyazaki F has been characterized by X-ray crystallography and absorption and resonance Raman spectroscopy. Nine crystal structures of the [NiFe]hydrogenase in the CO-bound and CO-liberated forms were determined at 1.2-1.4 A resolution. The exogenously added CO was assigned to be bound to the Ni atom at the Ni-Fe active site. The CO was not replaced with H(2) in the dark at 100 K, but was liberated by illumination with a strong white light. The Ni-C distances and Ni-C-O angles were about 1.77 A and 160 degrees, respectively, except for one case (1.72 A and 135 degrees ), in which an additional electron density peak between the CO and Sgamma(Cys546) was recognized. Distinct changes were observed in the electron density distribution of the Ni and Sgamma(Cys546) atoms between the CO-bound and CO-liberated structures for all the crystals tested. The novel structural features found near the Ni and Sgamma(Cys546) atoms suggest that these two atoms at the Ni-Fe active site play a role during the initial H(2)-binding process. Anaerobic addition of CO to dithionite-reduced [NiFe]hydrogenase led to a new absorption band at about 470 nm ( approximately 3000 M(-1)cm(-1)). Resonance Raman spectra (excitation at 476.5 nm) of the CO complex revealed CO-isotope-sensitive bands at 375/393 and 430 cm(-1) (368 and 413 cm(-1) for (13)C(18)O). The frequencies and relative intensities of the CO-related Raman bands indicated that the exogenous CO is bound to the Ni atom with a bent Ni-C-O structure in solution, in agreement with the refined structure determined by X-ray crystallography.
No preview · Article · Nov 2002 · Journal of the American Chemical Society