The structure of the Cu(A)-containing, extracellular domain of Thermus thermophilus ba3-type cytochrome c oxidase has been determined to 1.6 Å resolution using multiple X-ray wavelength anomalous dispersion (MAD). The Cu2S2 cluster forms a planar rhombus with a copper-copper distance of 2.51 ± 0.03 Å. X-ray absorption fine-structure (EXAFS) studies show that this distance is unchanged by crystallization. The Cu(A) center is asymmetrical; one copper is tetrahedrally coordinated to two bridging cysteine thiolates, one histidine nitrogen and one methionine sulfur, while the other is trigonally coordinated by the two cysteine thiolates and a histidine nitrogen. Combined sequence-structure alignment of amino acid sequences reveals conserved interactions between cytochrome c oxidase subunits I and II.
ASJC Scopus subject areas
- Structural Biology