Detection of two histidyl ligands to CuA of cytochrome oxidase by 35-GHz ENDOR. 14,15N and 63,65Cu ENDOR studies of the CuA site in bovine heart cytochrome aa3 and cytochromes caa3 and ba3 from Thermus thermophilus
| Autor: | Melanie M. Werst, Ryszard J. Gurbiel, Yang C. Fann, Sunney I. Chan, Kristene K. Surerus, Siegfried M. Musser, James A. Fee, Brian M. Hoffman, Peter E. Doan |
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| Rok vydání: | 1993 |
| Předmět: | |
| Zdroj: | Journal of the American Chemical Society. 115:10888-10894 |
| ISSN: | 1520-5126 0002-7863 |
| Popis: | To study the ligation of the Cu[sub A] site of heme-copper terminal oxidases, we have performed ENDOR measurements at X-band (9-GHz) and 35-GHz microwave frequencies on the three titled enzymes. The 35-GHz measurements provide complete spectral separation of the [sup 1]H and [sup 14]N resonances and permit analysis of the field dependence of the [sup 14]N ENDOR for each enzyme. The results indicate that two nitrogenous ligands were quite unequal hyperfine couplings are ligated to Cu[sub A] in each of the enzymes studied. We have also examined cytochrome caa[sub 3] isolated from His Thermus cells grown in the presence of D,L,-[[delta],[epsilon]-[sup 15]N[sub 2]]histidine. The 35-GHz Cu[sub A] ENDOR spectrum of this protein includes [sup 15]N ENDOR resonances whose frequencies confirm the presence of two nitrogeneous ligands; comparison with the [sup 14]N ENDOR spectra further shows that the ligand with the larger hyperfine coupling (N1) displays well-resolved [sup 14]N quadrupole splitting. The theory for simulating frozen-solution ENDOR spectra as refined here permits a determination of both hyperfine and quadrupole tensors for N1 of all three enzymes. These indicate that the bonding parameters and geometry of Cu[sub A] are well conserved. 55 refs., 7 figs., 1 tab. |
| Databáze: | OpenAIRE |
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