Structural highlights
Function
[NIFD_AZOVI] This molybdenum-iron protein is part of the nitrogenase complex that catalyzes the key enzymatic reactions in nitrogen fixation. [NIFK_AZOVI] This molybdenum-iron protein is part of the nitrogenase complex that catalyzes the key enzymatic reactions in nitrogen fixation.
Evolutionary Conservation
Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf.
Publication Abstract from PubMed
EPR signals observed under CO and C(2)H(2) during nitrogenase turnover were investigated for the alpha-Gln(195) MoFe protein, an altered form for which the alpha-His(195) residue has been substituted by glutamine. Under CO, samples show S = 1/2 hi- and lo-CO EPR signals identical to those recognized for the wild-type protein, whereas the S = 3/2 signals generated under high CO/high flux conditions differ. Previous work has revealed that the EPR spectrum generated under C(2)H(2) exhibits a signal (S(EPR1)) originating from the FeMo-cofactor having two or more bound C(2)H(2) adducts and a second signal (S(EPR2)) arising from a radical species [Sorlie, M., Christiansen, J., Dean, D. R., and Hales, B. J. (1999) J. Am. Chem. Soc. 121, 9457-9458]. Pressure-dependent studies show that the intensity of these signals has a sigmoidal dependency at low pressures and maximized at 0.1 atm C(2)H(2) with a subsequent decrease in steady-state intensity at higher pressures. Analogous signals are not recognized for the wild-type MoFe protein. Analysis of the principal g-factors of S(EPR2) suggests that it either represents an unusual metal cluster or is a carboxylate centered radical possibly originating from homocitrate. Both S(EPR1) and S(EPR2) exhibit similar relaxation properties that are atypical for S = 1/2 signals originating from Fe-S clusters or radicals and indicate a coupled relaxation pathway. The alpha-Gln(195) MoFe protein also exhibits these signals when incubated under turnover conditions in the presence of C(2)H(4). Under these conditions, additional inflections in the g 4-6 region assigned to ground-state transitions of an S = 3/2 spin system are also recognized and assigned to turnover states of the MoFe protein without C(2)H(4) bound. The structure of alpha-Gln(195) was crystallographically determined and found to be virtually identical to that of the wild-type MoFe protein except for replacement of an NuH-S hydrogen bond interaction between FeMo-cofactor and the imidazole side chain of alpha-His(195) by an analogous interaction involving Gln.
Mechanistic features and structure of the nitrogenase alpha-Gln195 MoFe protein.,Sorlie M, Christiansen J, Lemon BJ, Peters JW, Dean DR, Hales BJ Biochemistry. 2001 Feb 13;40(6):1540-9. PMID:11327812[1]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
See Also
References
- ↑ Sorlie M, Christiansen J, Lemon BJ, Peters JW, Dean DR, Hales BJ. Mechanistic features and structure of the nitrogenase alpha-Gln195 MoFe protein. Biochemistry. 2001 Feb 13;40(6):1540-9. PMID:11327812
