title: Structural redox control in a 7Fe ferredoxin isolated from Desulfovibrio alaskensis.
abstract: The redox behaviour of a ferredoxin (Fd) from Desulfovibrio alaskensis was characterized by electrochemistry. The protein was isolated and purified, and showed to be a tetramer containing one [3Fe-4S] and one [4Fe-4S] centre. This ferredoxin has high homology with FdI from Desulfovibrio vulgaris Miyazaki and Hildenborough and FdIII from Desulfovibrio africanus. From differential pulse voltammetry the following signals were identified: [3Fe-4S](+1/0) (E(0')=-158±5mV); [4Fe-4S](+2/+1) (E(0')=-474±5mV) and [3Fe-4S](0/-2) (E(0')=-660±5mV). The effect of pH on these signals showed that the reduced [3Fe-4S](0) cluster has a pK'(red)(')=5.1±0.1, the [4Fe-4S](+2/+1) centre is pH independent, and the [3Fe-4S](0/-2) reduction is accompanied by the binding of two protons. The ability of the [3Fe-4S](0) cluster to be converted into a new [4Fe-4S] cluster was proven. The redox potential of the original [4Fe-4S] centre showed to be dependent on the formation of the new [4Fe-4S] centre, which results in a positive shift (ca. 70mV) of the redox potential of the original centre. Being most [Fe-S] proteins involved in electron transport processes, the electrochemical characterization of their clusters is essential to understand their biological function. Complementary EPR studies were performed.
authors: REQUIMTE/CQFB, Departamento de Química, Universidade Nova de Lisboa, Caparica, Portugal. raquel.grazina@dq.fct.unl.pt
authors: Raquel
authors: R
authors: Grazina
authors: Patrícia M Paes
authors: PM
authors: de Sousa
authors: Carlos D
authors: CD
authors: Brondino
authors: Marta S P
authors: MS
authors: Carepo
authors: Isabel
authors: I
authors: Moura
authors: José J G
authors: JJ
authors: Moura