scholarly journals [3Fe-4S]↔[4Fe-4S] cluster interconversion in Desulfovibrio africanus ferredoxin III: properties of an Asp14→Cys mutant

1997 ◽  
Vol 323 (1) ◽  
pp. 95-102 ◽  
Author(s):  
Johanneke L. H. BUSCH ◽  
Jacques L. BRETON ◽  
Barry M. BARTLETT ◽  
Fraser A. ARMSTRONG ◽  
Richard JAMES ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Cluster Analysis ◽  
Spin State ◽  
Magnetic Circular Dichroism ◽  
Cysteine Residue ◽  
Mutant Protein ◽  
Native Protein ◽  
Ground Spin State ◽  
Aspartate Residue ◽  
Reduced State

The 8Fe ferredoxin III from Desulfovibrio africanus is a monomeric protein which contains two [4Fe-4S]2+/1+ clusters, one of which is labile and can readily and reversibly lose one Fe under oxidative conditions to yield a [3Fe-4S]1+/0 cluster. This 4Fe cluster has an S = 3/2 ground spin state instead of S = 1/2 in the reduced +1 state [George, Armstrong, Hatchikian and Thomson (1989) Biochem. J.264, 275-284]. The co-ordination to this cluster is unusual in that an aspartate (Asp14, D14) is found where a cysteine residue normally occurs. Using a mutant protein obtained from the overexpression in Escherichia coli of a synthetic gene in which Asp14, the putative ligand to the removable Fe, has been changed to Cys, we have studied the cluster interconversion properties of the labile cluster. Analysis by EPR and magnetic-circular-dichroism spectroscopies showed that the Asp14 → Cys (D14C) mutant contains two [4Fe-4S]2+/1+ clusters, both with S = 1/2 in the reduced state. Also, unlike in native 8Fe D. africanus ferredoxin III, the 4Fe ↔ 3Fe cluster interconversion reaction was found to be sluggish and did not go to completion. It is inferred that the reversibility of the reaction in the native protein is due to the presence of the aspartate residue at position 14 and that this residue might protect the [3Fe-4S] cluster from further degradation.

scholarly journals Structure of Escherichia coli dnaC. Identification of a cysteine residue possibly involved in association with dnaB protein.

1987 ◽  
Vol 262 (22) ◽  
pp. 10475-10480 ◽  
Author(s):  
N Nakayama ◽  
M W Bond ◽  
A Miyajima ◽  
J Kobori ◽  
K Arai
Keyword(s):  
Escherichia Coli ◽  
Cysteine Residue

Ground Spin State Variation in Carboxylate-Bridged Tetranuclear [Fe2Mn2O2]8+ Cores and a Comparison with Their [Fe4O2]8+ and [Mn4O2]8+ Congeners

2003 ◽  
Vol 2003 (3) ◽  
pp. 541-555 ◽  
Author(s):  
Phalguni Chaudhuri ◽  
Eva Rentschler ◽  
Frank Birkelbach ◽  
Carsten Krebs ◽  
Eckhard Bill ◽  
...  
Keyword(s):  
Spin State ◽  
State Variation ◽  
Ground Spin State

scholarly journals Competitive binding of MatP and topoisomerase IV to the MukB dimerization hinge

2021 ◽  
Author(s):  
Gemma L. M. Fisher ◽  
Jani R. Bolla ◽  
Karthik V. Rajasekar ◽  
Jarno Mäkelä ◽  
Rachel Baker ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Competitive Binding ◽  
Mutant Protein ◽  
Chromosomal Distribution ◽  
Topoisomerase Iv ◽  
Binding Interface ◽  
Cellular Localisation ◽  
Chromosome Organisation

ABSTRACTSMC complexes have ubiquitous roles in chromosome organisation. In Escherichia coli, the interplay between the SMC complex, MukBEF, and matS-bound MatP in the replication termination region, ter, results in depletion of MukBEF from ter, thus promoting chromosome individualisation by directing replichores to separate cell halves. MukBEF also interacts with topoisomerase IV ParC2E2 heterotetramers, to direct its chromosomal distribution to mirror that of MukBEF, thereby facilitating coordination between chromosome organisation and decatenation by topoisomerase IV. Here we demonstrate that the MukB dimerization hinge binds ParC and MatP with the same dimer to dimer stoichiometry. MatP and ParC have an overlapping binding interface on the MukB hinge, leading to their mutually exclusive binding. Furthermore, the MukB hinge fails to stably associate with matS-bound MatP, while MatP mutants deficient in matS binding are impaired in MukB hinge binding, demonstrating that mats competes with the hinge for MatP binding. Cells expressing MukBEF complexes containing a mutation in the MukB hinge interface for ParC/MatP binding are deficient in ParC binding in vivo, despite having a Muk+ topoisomerase IV+ phenotype. This mutant protein is also impaired in MatP binding in vitro, and cells expressing this variant exhibit a MukBEF cellular localisation consistent with impaired MatP binding.

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