Modulation of the redox potential of the [Fe(SCys)(4)] site in rubredoxin by the orientation of a peptide dipole.

Ala44 exchange mutants, [V44A]Cp and [A44V]Pf Rds, have been cloned and expressed. Reduction potentials of these residue 44 variants and pertinent features of the X-ray crystal structure of [V44A]Cp Rd are reported. Relative to those of wild-type Cp and Pf Rds, the V44A mutation in Cp Rd results in an 86 mV increase in midpoint reduction potential and the [A44V] mutation in Pf Rd results in a 95 mV decrease in midpoint reduction potential, respectively. In the crystal structure of [V44A]Cp Rd, the peptide bond between residues 43 and 44 is approximately 0.3 A closer to the Fe center and the hydrogen bond distance between the residue 44 peptide nitrogen and the Cys42 gamma-sulfur decreases by 0.32 A compared to the analogous distances in the wild-type Cp Rd crystal structure. The results described herein support the prediction that the identity of residue 44 alone determines whether a Rd reduction potential of about -50 or 0 mV is observed. -->
Grant Information: GM45303 United States GM NIGMS NIH HHS; GM50736 United States GM NIGMS NIH HHS; GM59030-01 United States GM NIGMS NIH HHS; etc.
Substance Nomenclature: 0 (Bacterial Proteins)
0 (Peptides)
0 (Rubredoxins)
138635-16-2 (rubredoxin protein, Clostridium pasteurianum)
Entry Date(s): Date Created: 19991111 Date Completed: 19991220 Latest Revision: 20190613
Update Code: 20240829
DOI: 10.1021/bi991661f
PMID: 10555962
Autor: Eidsness MK; Department of Chemistry and Center for Metalloenzyme Studies, University of Georgia, Athens, Georgia 30602-2556, USA. eidsness@uga.edu, Burden AE, Richie KA, Kurtz DM Jr, Scott RA, Smith ET, Ichiye T, Beard B, Min T, Kang C
Jazyk: angličtina
Zdroj: Biochemistry [Biochemistry] 1999 Nov 09; Vol. 38 (45), pp. 14803-9.
DOI: 10.1021/bi991661f
Abstrakt: Rubredoxins (Rds) may be separated into two classes based upon the correlation of their reduction potentials with the identity of residue 44; those with Ala44 have reduction potentials that are approximately 50 mV higher than those with Val44. The smaller side chain volume occupied by Ala44 relative to that occupied by Val44 has been proposed to explain the increase in the reduction potential, based upon changes in the Gly43-Ala44 peptide bond orientation and the distance to the [Fe(SCys)(4)] center in the Pyrococcus furiosus (Pf) Rd crystal structure compared to those of Gly43-Val44 in the Clostridium pasteurianum (Cp) Rd crystal structure. As an experimental test of this hypothesis, single-site Val44 <--> Ala44 exchange mutants, [V44A]Cp and [A44V]Pf Rds, have been cloned and expressed. Reduction potentials of these residue 44 variants and pertinent features of the X-ray crystal structure of [V44A]Cp Rd are reported. Relative to those of wild-type Cp and Pf Rds, the V44A mutation in Cp Rd results in an 86 mV increase in midpoint reduction potential and the [A44V] mutation in Pf Rd results in a 95 mV decrease in midpoint reduction potential, respectively. In the crystal structure of [V44A]Cp Rd, the peptide bond between residues 43 and 44 is approximately 0.3 A closer to the Fe center and the hydrogen bond distance between the residue 44 peptide nitrogen and the Cys42 gamma-sulfur decreases by 0.32 A compared to the analogous distances in the wild-type Cp Rd crystal structure. The results described herein support the prediction that the identity of residue 44 alone determines whether a Rd reduction potential of about -50 or 0 mV is observed.
Databáze: MEDLINE
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