TY - JOUR
T1 - Strong excitonic interactions in the oxygen-reducing site of bd-type oxidase
T2 - The Fe-to-Fe distance between hemes d and b595 is 10 Å
AU - Arutyunyan, Alexander M.
AU - Borisov, Vitaliy B.
AU - Novoderezhkin, Vladimir I.
AU - Ghaim, Josh
AU - Zhang, Jie
AU - Gennis, Robert B.
AU - Konstantinov, Alexander A.
PY - 2008/2/12
Y1 - 2008/2/12
N2 - Absorption and circular dichroism (CD) spectra of cytochrome bd from Escherichia coli have been compared for the wild type enzyme and an inactive mutant in which a highly conserved E445 in subunit I has been replaced by alanine [Zhang, J., Hellwig, P., Osborne, J. P., Huang, H. W., Moenne-Loccoz, P., Konstantinov, A. A., and Gennis, R. B. (2001) Biochemistry 40, 8548-8556]. The absorption bands of ferrous heme b595 are absent from the spectrum of the dithionite-reduced E445A form of cytochrome bd. The difference between the spectra of the dithionite-reduced WT and E445A enzymes indicates that in the mutant, heme b595 is present but is not reducible by dithionite. Cytochrome bd reveals intense CD signals dominated by heme d, with almost no contribution from heme b595 or heme b558. The CD spectrum of the reduced wild type enzyme in the Soret band indicates strong excitonic interactions between ferrous heme d and ferrous heme b595, and these interactions are not observed in dithionite-reduced E445A mutant, in which heme b595 remains in the ferric state. Modeling the excitonic interactions in both absorption and CD spectra has been carried out, yielding an estimate of the Fe-to-Fe distance between heme d and heme b595 of about 10 Å. The physical proximity supports the hypothesis that heme d and heme b595 can form a di-heme oxygen reducing site, a unique structure for respiratory oxidases.
AB - Absorption and circular dichroism (CD) spectra of cytochrome bd from Escherichia coli have been compared for the wild type enzyme and an inactive mutant in which a highly conserved E445 in subunit I has been replaced by alanine [Zhang, J., Hellwig, P., Osborne, J. P., Huang, H. W., Moenne-Loccoz, P., Konstantinov, A. A., and Gennis, R. B. (2001) Biochemistry 40, 8548-8556]. The absorption bands of ferrous heme b595 are absent from the spectrum of the dithionite-reduced E445A form of cytochrome bd. The difference between the spectra of the dithionite-reduced WT and E445A enzymes indicates that in the mutant, heme b595 is present but is not reducible by dithionite. Cytochrome bd reveals intense CD signals dominated by heme d, with almost no contribution from heme b595 or heme b558. The CD spectrum of the reduced wild type enzyme in the Soret band indicates strong excitonic interactions between ferrous heme d and ferrous heme b595, and these interactions are not observed in dithionite-reduced E445A mutant, in which heme b595 remains in the ferric state. Modeling the excitonic interactions in both absorption and CD spectra has been carried out, yielding an estimate of the Fe-to-Fe distance between heme d and heme b595 of about 10 Å. The physical proximity supports the hypothesis that heme d and heme b595 can form a di-heme oxygen reducing site, a unique structure for respiratory oxidases.
UR - http://www.scopus.com/inward/record.url?scp=38949194251&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=38949194251&partnerID=8YFLogxK
U2 - 10.1021/bi701884g
DO - 10.1021/bi701884g
M3 - Article
C2 - 18205406
AN - SCOPUS:38949194251
SN - 0006-2960
VL - 47
SP - 1752
EP - 1759
JO - Biochemistry
JF - Biochemistry
IS - 6
ER -