4RKN
Wolinella succinogenes octaheme sulfite reductase MccA, form II
Summary for 4RKN
| Entry DOI | 10.2210/pdb4rkn/pdb |
| Related | 4RKM |
| Descriptor | MccA, DITHIONITE, PROTOPORPHYRIN IX CONTAINING FE, ... (6 entities in total) |
| Functional Keywords | multiheme cytochrome c, sulfite reductase, periplasmic, unknown function |
| Biological source | Wolinella succinogenes DSM 1740 |
| Cellular location | Periplasm : Q7MSJ8 |
| Total number of polymer chains | 4 |
| Total formula weight | 349373.53 |
| Authors | Hermann, B.,Kern, M.,La Pietra, L.,Simon, J.,Einsle, O. (deposition date: 2014-10-13, release date: 2015-02-04, Last modification date: 2024-10-16) |
| Primary citation | Hermann, B.,Kern, M.,La Pietra, L.,Simon, J.,Einsle, O. The octahaem MccA is a haem c-copper sulfite reductase. Nature, 520:706-709, 2015 Cited by PubMed Abstract: The six-electron reduction of sulfite to sulfide is the pivot point of the biogeochemical cycle of the element sulfur. The octahaem cytochrome c MccA (also known as SirA) catalyses this reaction for dissimilatory sulfite utilization by various bacteria. It is distinct from known sulfite reductases because it has a substantially higher catalytic activity and a relatively low reactivity towards nitrite. The mechanistic reasons for the increased efficiency of MccA remain to be elucidated. Here we show that anoxically purified MccA exhibited a 2- to 5.5-fold higher specific sulfite reductase activity than the enzyme isolated under oxic conditions. We determined the three-dimensional structure of MccA to 2.2 Å resolution by single-wavelength anomalous dispersion. We find a homotrimer with an unprecedented fold and haem arrangement, as well as a haem bound to a CX15CH motif. The heterobimetallic active-site haem 2 has a Cu(I) ion juxtaposed to a haem c at a Fe-Cu distance of 4.4 Å. While the combination of metals is reminiscent of respiratory haem-copper oxidases, the oxidation-labile Cu(I) centre of MccA did not seem to undergo a redox transition during catalysis. Intact MccA tightly bound SO2 at haem 2, a dehydration product of the substrate sulfite that was partially turned over due to photoreduction by X-ray irradiation, yielding the reaction intermediate SO. Our data show the biometal copper in a new context and function and provide a chemical rationale for the comparatively high catalytic activity of MccA. PubMed: 25642962DOI: 10.1038/nature14109 PDB entries with the same primary citation |
| Experimental method | X-RAY DIFFRACTION (2.1 Å) |
Structure validation
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