Abstract/Details

Structure determination and refinement at 2.2 angstroms of nitrogenase molybdenum iron-protein from Clostridium pasteurianum


1994 1994

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Abstract (summary)

Nitrogenase catalyzes the reduction of dinitrogen through the activity of a complex of two easily separated components known as the MoFe-protein and the Fe-protein. The MoFe-protein is the site of N$\sb2$ binding and reduction, whereas the Fe-protein provides electrons and binds ATP.

MoFe-protein is a large (M$\sb{\rm r}$ = 230,000), $\alpha\sb2\beta\sb2$, tetrameric enzyme that contains two copies each of two unusual metal clusters known as the FeMo-cofactor and the P-cluster. The crystal structure of MoFe-protein from Clostridium pasteurianum has been determined to 2.2A resolution by a combination of phasing methods including multiwavelength anomalous diffraction, isomorphous replacement, and phase extension involving both solvent flattening and molecular averaging. Both rotating anode and synchrotron (SSRL, CHESS, and Photon Factory) sources were used for diffraction experiments at a variety of wavelengths including 1.0A, 1.54A, 1.74A, and 1.79A.

An atomic model of MoFe-protein, with its bound metal-sulfur clusters, 2 Mg$\sp{2+}$ ions, and 1,004 water molecules, has been refined by least-squares techniques against crystallographic data and stereochemical restraints. The refined model has an R-factor of 15.1% based on all measured crystallographic data between 25A and 2.2A. The protein model has root mean-square deviations from ideal bond distances and angles of 0.006A and 1.67$\sp\circ$, respectively.

The crystalloeraphic results are interpreted with respect to the chemical mechanism of N$\sb2$ reduction and intramolecular electron transfer.

Indexing (details)


Subject
Biochemistry;
Biophysics
Classification
0487: Biochemistry
0786: Biophysics
Identifier / keyword
Pure sciences; Biological sciences; iron; molybdenum iron protein
Title
Structure determination and refinement at 2.2 angstroms of nitrogenase molybdenum iron-protein from Clostridium pasteurianum
Author
Campobasso, Nino
Number of pages
192
Publication year
1994
Degree date
1994
School code
0183
Source
DAI-B 56/02, Dissertation Abstracts International
Place of publication
Ann Arbor
Country of publication
United States
Advisor
Bolin, Jeffrey Temple
University/institution
Purdue University
University location
United States -- Indiana
Degree
Ph.D.
Source type
Dissertations & Theses
Language
English
Document type
Dissertation/Thesis
Dissertation/thesis number
9523320
ProQuest document ID
304119657
Copyright
Database copyright ProQuest LLC; ProQuest does not claim copyright in the individual underlying works.
Document URL
http://search.proquest.com/docview/304119657/abstract
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