title: Monothiol glutaredoxins function in storing and transporting [Fe2S2] clusters assembled on IscU scaffold proteins.
abstract: In the bacterial ISC system for iron-sulfur cluster assembly, IscU acts as a primary scaffold protein, and the molecular co-chaperones HscA and HscB specifically interact with IscU to facilitate ATP-driven cluster transfer. In this work, cluster transfer from Azotobacter vinelandii [Fe(2)S(2)](2+) cluster-bound IscU to apo-Grx5, a general purpose monothiol glutaredoxin in A. vinelandii, was monitored by circular dichroism spectroscopy, in the absence and in the presence of HscA/HscB/Mg-ATP. The results indicate a 700-fold enhancement in the rate of [Fe(2)S(2)](2+) cluster transfer in the presence of the co-chaperones and Mg-ATP, yielding a second-order rate constant of 20 000 M(-1) min(-1) at 23 °C. Thus, HscA and HscB are required for efficient ATP-dependent [Fe(2)S(2)](2+) cluster transfer from IscU to Grx5. The results support a role for monothiol Grx's in storing and transporting [Fe(2)S(2)](2+) clusters assembled on IscU and illustrate the limitations of interpreting in vitro cluster transfer studies involving [Fe(2)S(2)]-IscU in the absence of the dedicated HscA/HscB co-chaperone system.
authors.affiliation: Department of Chemistry and Center for Metalloenzyme Studies, University of Georgia, Athens, Georgia 30602, USA.
authors.forename: Priyanka
authors.initials: P
authors.lastname: Shakamuri
authors.forename: Bo
authors.initials: B
authors.lastname: Zhang
authors.forename: Michael K
authors.initials: MK
authors.lastname: Johnson
mesh_terms: D002942:Circular Dichroism; D054477:Glutaredoxins / Q000737:chemistry / Q000502:physiology*; D007506:Iron-Sulfur Proteins / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet; D013438:Sulfhydryl Compounds / Q000737:chemistry*
chemical_list: D054477:Glutaredoxins; D007506:Iron-Sulfur Proteins; D013438:Sulfhydryl Compounds