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| | {{STRUCTURE_1fp4| PDB=1fp4 | SCENE= }} | | {{STRUCTURE_1fp4| PDB=1fp4 | SCENE= }} |
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| - | '''CRYSTAL STRUCTURE OF THE ALPHA-H195Q MUTANT OF NITROGENASE'''
| + | ===CRYSTAL STRUCTURE OF THE ALPHA-H195Q MUTANT OF NITROGENASE=== |
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| - | ==Overview==
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| - | 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.
| + | The line below this paragraph, {{ABSTRACT_PUBMED_11327812}}, adds the Publication Abstract to the page |
| | + | (as it appears on PubMed at http://www.pubmed.gov), where 11327812 is the PubMed ID number. |
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| | + | {{ABSTRACT_PUBMED_11327812}} |
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| | ==About this Structure== | | ==About this Structure== |
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| | [[Category: Sorlie, M.]] | | [[Category: Sorlie, M.]] |
| | [[Category: Iron-sulfur-molybdenum protein]] | | [[Category: Iron-sulfur-molybdenum protein]] |
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 16:35:57 2008'' | + | |
| | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 1 03:43:14 2008'' |
Revision as of 00:43, 1 July 2008
Template:STRUCTURE 1fp4
CRYSTAL STRUCTURE OF THE ALPHA-H195Q MUTANT OF NITROGENASE
Template:ABSTRACT PUBMED 11327812
About this Structure
1FP4 is a Protein complex structure of sequences from Azotobacter vinelandii. Full crystallographic information is available from OCA.
Reference
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
Page seeded by OCA on Tue Jul 1 03:43:14 2008
