8H8S

Calcium-bound structure of bovine cytochrome c oxidase.

(2023) Biochim Biophys Acta Bioenerg 1864: 148956-148956

• PubMed: 36708913 Search on PubMed
• DOI: https://doi.org/10.1016/j.bbabio.2023.148956
• Primary Citation of Related Structures:  
  8H8R, 8H8S


• PubMed Abstract: 
  

  The crystal structure of bovine cytochrome c oxidase (CcO) shows a sodium ion (Na ⁺ ) bound to the surface of subunit I. Changes in the absorption spectrum of heme a caused by calcium ions (Ca ²⁺ ) are detected as small red shifts, and inhibition of enzymatic activity under low turnover conditions is observed by addition of Ca ²⁺ in a competitive manner with Na ⁺ . In this study, we determined the crystal structure of Ca ²⁺ -bound bovine CcO in the oxidized and reduced states at 1.7?? resolution. Although Ca ²⁺ and Na ⁺ bound to the same site of oxidized and reduced CcO, they led to different coordination geometries. Replacement of Na ⁺ with Ca ²⁺ caused a small structural change in the loop segments near the heme a propionate and formyl groups, resulting in spectral changes in heme a. Redox-coupled structural changes observed in the Ca ²⁺ -bound form were the same as those previously observed in the Na ⁺ -bound form, suggesting that binding of Ca ²⁺ does not severely affect enzymatic function, which depends on these structural changes. The relation between the Ca ²⁺ binding and the inhibitory effect during slow turnover, as well as the possible role of bound Ca ²⁺ are discussed.

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Organizational Affiliation: 

Graduate School of Science, University of Hyogo, 3-2-1 Kouto, Kamigori, Ako, Hyogo 678-1297, Japan. Electronic address: muramoto@sci.u-hyogo.ac.jp.