Probing the MgATP-Bound Conformation of the Nitrogenase Fe Protein By Solution Small-Angle X-Ray Scattering

Journal Article · Thu Apr 30 04:00:00 EDT 2009 · Biochem.46:14058-14066,2007

OSTI ID:958652

Sarma, R; Mulder, D W; Brecht, E; Szilagyi, R K; Seefeldt, L C; Tsuruta, H; Peters, J W

The MgATP-bound conformation of the Fe protein of nitrogenase from Azotobacter vinelandii has been examined in solution by small-angle X-ray scattering (SAXS) and compared to existing crystallographically characterized Fe protein conformations. The results of the analysis of the crystal structure of an Fe protein variant with a Switch II single-amino acid deletion recently suggested that the MgATP-bound state of the Fe protein may exist in a conformation that involves a large-scale reorientation of the dimer subunits, resulting in an overall elongated structure relative to the more compact structure of the MgADP-bound state. It was hypothesized that the Fe protein variant may be a conformational mimic of the MgATP-bound state of the native Fe protein largely on the basis of the observation that the spectroscopic properties of the [4Fe-4S] cluster of the variant mimicked in part the spectroscopic signatures of the native nitrogenase Fe protein in the MgATP-bound state. In this work, SAXS studies reveal that the large-scale conformational differences between the native Fe protein and the variant observed by X-ray crystallography are also observed in solution. In addition, comparison of the SAXS curves of the Fe protein nucleotide-bound states to the nucleotide-free states indicates that the conformation of the MgATP-bound state in solution does not resemble the structure of the variant as initially proposed, but rather, at the resolution of this experiment, it resembles the structure of the nucleotide-free state. These results provide insights into the Fe protein conformations that define the role of MgATP in nitrogenase catalysis.

• Research Organization: Stanford Linear Accelerator Center (SLAC)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC02-76SF00515
• OSTI ID: 958652
• Report Number(s): SLAC-REPRINT-2009-029
• Journal Information: Biochem.46:14058-14066,2007, Journal Name: Biochem.46:14058-14066,2007 Journal Issue: 49 Vol. 46; ISSN 0006-2960; ISSN BICHAW
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
AZOTOBACTER
BIO
CHEM
CATALYSIS
CRYSTAL STRUCTURE
CRYSTALLOGRAPHY
DIMERS
NITROGENASE
PROTEINS
RESOLUTION
SCATTERING