Solution NMR Characterization of the Thermodynamics of the Disulfide Bond Orientational Isomerism and Its Effect of Cluster Electronic Properties for the Hyperthermostable Three-Iron Cluster Ferredoxi
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- 作者：Mateus Webba da Silva ; Simon Sham ; Carol M. Gorst ; Luigi Calzolai ; Philip S. Brereton ; Michael W. W. Adams ; and Gerd N. La Mar
- 刊名：Biochemistry
- 出版年：2001
- 出版时间：October 23, 2001
- 年：2001
- 卷：40
- 期：42
- 页码：12575 - 12583
- 全文大小：139K
- 年卷期：v.40,no.42(October 23, 2001)
- ISSN：1520-4995
文摘
The thermodynamics and dynamics of the Cys21-Cys48 disulfide "S" 
"R" conformationalisomerism in the three-iron, single cubane cluster ferredoxin (Fd) from the hyperthermophilic archaeonPyrococcus furiosus (Pf) have been characterized by 1H NMR spectroscopy in both water and water/methanol mixed solvents. The mean interconversion rate at 25 
C is 3 × 103 s-1 and 
G298 = -0.2kcal/mol [H = 4.0 kcal/mol; S = 14 cal/(mol·K)], with the S orientation as the more stable form atlow temperature (<0 C) but the R orientation predominating at >100 C, where the organism thrives.The distinct pattern of ligated Cys 
-proton contact shifts for the resolved signals and their characteristictemperature behavior for the forms of the 3Fe Fd with alternate disulfide orientations have been analyzedto determine the influences of disulfide orientation and methanol cosolvent on the topology of the inter-iron spin coupling in the 3Fe cluster. The Cys21-Cys48 disulfide orientation influences primarily thespin couplings involving the iron ligated to Cys17, whose carbonyl oxygen is a hydrogen bond acceptorto the Cys21 peptide proton. Comparison of the Cys -proton contact shift pattern for the alternate disulfideorientations with the pattern exhibited upon cleaving the disulfide bridge confirms an earlier [Wang,P.-L., Calzolai, L., Bren, K. L., Teng, Q., Jenney, F. E., Jr., Brereton, P. S., Howard, J. B., Adams, M.W. W., and La Mar, G. N. (1999) Biochemistry 38, 8167-8178] proposal that the structure of the sameFd with the R disulfide orientation resembles that of the Fd upon cleaving the disulfide bond.
"R" conformationalisomerism in the three-iron, single cubane cluster ferredoxin (Fd) from the hyperthermophilic archaeonPyrococcus furiosus (Pf) have been characterized by 1H NMR spectroscopy in both water and water/methanol mixed solvents. The mean interconversion rate at 25 C is 3 × 103 s-1 and G298 = -0.2kcal/mol [H = 4.0 kcal/mol; S = 14 cal/(mol·K)], with the S orientation as the more stable form atlow temperature (<0 C) but the R orientation predominating at >100 C, where the organism thrives.The distinct pattern of ligated Cys -proton contact shifts for the resolved signals and their characteristictemperature behavior for the forms of the 3Fe Fd with alternate disulfide orientations have been analyzedto determine the influences of disulfide orientation and methanol cosolvent on the topology of the inter-iron spin coupling in the 3Fe cluster. The Cys21-Cys48 disulfide orientation influences primarily thespin couplings involving the iron ligated to Cys17, whose carbonyl oxygen is a hydrogen bond acceptorto the Cys21 peptide proton. Comparison of the Cys -proton contact shift pattern for the alternate disulfideorientations with the pattern exhibited upon cleaving the disulfide bridge confirms an earlier [Wang,P.-L., Calzolai, L., Bren, K. L., Teng, Q., Jenney, F. E., Jr., Brereton, P. S., Howard, J. B., Adams, M.W. W., and La Mar, G. N. (1999) Biochemistry 38, 8167-8178] proposal that the structure of the sameFd with the R disulfide orientation resembles that of the Fd upon cleaving the disulfide bond.