A proposed role for the Azotobacter vinelandii NfuA protein as an intermediate iron-sulfur cluster carrier.
Iron-sulfur clusters ([Fe-S] clusters) are assembled on molecular scaffolds and subsequently used for maturation of proteins that require [Fe-S] clusters for their functions. Previous studies have shown that Azotobacter vinelandii produces at least two [Fe-S] cluster assembly scaffolds: NifU, required for the maturation of nitrogenase, and IscU, required for the general maturation of other [Fe-S] proteins. A. vinelandii also encodes a protein designated NfuA, which shares amino acid sequence similarity with the C-terminal region of NifU. The activity of aconitase, a [4Fe-4S] cluster-containing enzyme, is markedly diminished in a strain containing an inactivated nfuA gene. This inactivation also results in a null-growth phenotype when the strain is cultivated under elevated oxygen concentrations. NifU has a limited ability to serve the function of NfuA, as its expression at high levels corrects the defect of the nfuA-disrupted strain. Spectroscopic and analytical studies indicate that one [4Fe-4S] cluster can be assembled in vitro within a dimeric form of NfuA. The resultant [4Fe-4S] cluster-loaded form of NfuA is competent for rapid in vitro activation of apo-aconitase. Based on these results a model is proposed where NfuA could represent a class of intermediate [Fe-S] cluster carriers involved in [Fe-S] protein maturation.
Bandyopadhyay
Sibali
S
Department of Chemistry, University of Georgia, Athens, Georgia 30602, USA.
Naik
Sunil G
SG
O'Carroll
Ina P
IP
Huynh
Boi-Hanh
BH
Dean
Dennis R
DR
Johnson
Michael K
MK
Dos Santos
Patricia C
PC
D000154:Aconitate Hydratase / Q000737:chemistry; D016948:Azotobacter vinelandii / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism; D049109:Cell Proliferation; D007501:Iron / Q000737:chemistry; D007506:Iron-Sulfur Proteins / Q000737:chemistry / Q000502:physiology*; D008954:Models, Biological; D010100:Oxygen / Q000737:chemistry; D010641:Phenotype; D017434:Protein Structure, Tertiary; D013053:Spectrophotometry / Q000379:methods; D013056:Spectrophotometry, Ultraviolet / Q000379:methods; D015204:Spectroscopy, Mossbauer; D013455:Sulfur / Q000737:chemistry
D007506:Iron-Sulfur Proteins; D013455:Sulfur; D007501:Iron; D000154:Aconitate Hydratase; D010100:Oxygen