Incorporation of molybdenum into the iron-molybdenum cofactor of nitrogenase.
The biosynthesis of the iron-molybdenum cofactor (FeMo-co) of dinitrogenase was investigated using 99Mo to follow the incorporation of Mo into precursors. 99Mo label accumulates on dinitrogenase only when all known components of the FeMo-co synthesis system, NifH, NifNE, NifB-cofactor, homocitrate, MgATP, and reductant, are present. Furthermore, 99Mo label accumulates only on the gamma protein, which has been shown to serve as a chaperone/insertase for the maturation of apodinitrogenase when all known components are present. It appears that only completed FeMo-co can accumulate on the gamma protein. Very little FeMo-co synthesis was observed when all known components are used in purified forms, indicating that additional factors are required for optimal FeMo-co synthesis. 99Mo did not accumulate on NifNE under any conditions tested, suggesting that Mo enters the pathway at some other step, although it remains possible that a Mo-containing precursor of FeMo-co that is not sufficiently stable to persist during gel electrophoresis occurs but is not observed. 99Mo accumulates on several unidentified species, which may be the additional components required for FeMo-co synthesis. The molybdenum storage protein was observed and the accumulation of 99Mo on this protein required nucleotide.
Allen
R M
RM
Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 53706, USA.
Roll
J T
JT
Rangaraj
P
P
Shah
V K
VK
Roberts
G P
GP
Ludden
P W
PW
D000255:Adenosine Triphosphate / Q000378:metabolism; D016948:Azotobacter vinelandii / Q000201:enzymology* / Q000235:genetics; D001426:Bacterial Proteins / Q000737:chemistry; D003013:Clostridium / Q000201:enzymology; D015394:Molecular Structure; D008982:Molybdenum / Q000737:chemistry*; D008983:Molybdoferredoxin / Q000096:biosynthesis* / Q000737:chemistry; D009591:Nitrogenase / Q000737:chemistry* / Q000378:metabolism; D009711:Nucleotides / Q000378:metabolism; D010088:Oxidoreductases
D001426:Bacterial Proteins; D008983:Molybdoferredoxin; D009711:Nucleotides; D008982:Molybdenum; D000255:Adenosine Triphosphate; D010088:Oxidoreductases; D009591:Nitrogenase; C029130:nitrogenase reductase