4RKN

Wolinella succinogenes octaheme sulfite reductase MccA, form II

4RKN の概要

• エントリーDOI: 10.2210/pdb4rkn/pdb
• 関連するPDBエントリー: 4RKM
• 分子名称: MccA, DITHIONITE, PROTOPORPHYRIN IX CONTAINING FE, ... (6 entities in total)
• 機能のキーワード: multiheme cytochrome c, sulfite reductase, periplasmic, unknown function
• 由来する生物種: Wolinella succinogenes DSM 1740
• 細胞内の位置: Periplasm : Q7MSJ8
• タンパク質・核酸の鎖数: 4
• 化学式量合計: 349373.53

構造登録者

Hermann, B.,Kern, M.,La Pietra, L.,Simon, J.,Einsle, O. (登録日: 2014-10-13, 公開日: 2015-02-04, 最終更新日: 2024-10-16)

主引用文献

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

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: 25642962
DOI: 10.1038/nature14109

実験手法

X-RAY DIFFRACTION (2.1 Å)