In vivo iron-sulfur cluster formation.
It has been proposed that iron-sulfur [Fe-S] clusters destined for the maturation of [Fe-S] proteins can be preassembled on a molecular scaffold designated IscU. In the present article, it is shown that production of the intact Azotobacter vinelandii [Fe-S] cluster biosynthetic machinery at levels exceeding the amount required for cellular maturation of [Fe-S] proteins results in the accumulation of: (i) apo-IscU, (ii) an oxygen-labile [2Fe-2S] cluster-loaded form of IscU, and (iii) IscU complexed with the S-delivery protein, IscS. It is suggested that these species represent different stages of the [Fe-S] cluster assembly process. Substitution of the IscU Asp(39) residue by Ala results in the in vivo trapping of a stoichiometric, noncovalent, nondissociating IscU-IscS complex that contains an oxygen-resistant [Fe-S] species. In aggregate, these results validate the scaffold hypothesis for [Fe-S] cluster assembly and indicate that in vivo [Fe-S] cluster formation is a dynamic process that involves the reversible interaction of IscU and IscS.
Raulfs
Estella C
EC
Department of Biochemistry, Virginia Tech, Blacksburg, VA 24061, USA.
O'Carroll
Ina P
IP
Dos Santos
Patricia C
PC
Unciuleac
Mihaela-Carmen
MC
Dean
Dennis R
DR
D016948:Azotobacter vinelandii / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism*; D013437:Carbon-Sulfur Lyases / Q000378:metabolism; D007506:Iron-Sulfur Proteins / Q000378:metabolism*; D007700:Kinetics; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism
D001426:Bacterial Proteins; D007506:Iron-Sulfur Proteins; D021122:Protein Subunits; D013437:Carbon-Sulfur Lyases; C080546:cysteine desulfurase