title: The molybdenum--iron protein of Klebsiella pneumoniae nitrogenase. Evidence for non-identical subunits from peptide 'mapping'.
abstract: The molybdenum- and iron-containing protein components of nitrogenase purified from Klebsiella pneumoniae, Azotobacter vinelandii, Azotobacter chroococcum and Rhizobium japonicum bacteroids all gave either one or two protein-staining bands after sodium dodecyl sulphate/polyacrylamide-gel electrophoresis, depending on the commercial brand of sodium dodecyl sulphate used. The single band obtained with K. pneumoniae Mo-Fe protein when some commercial brands of sodium dodecyl sulphate were used in the preparation of the electrode buffer was resolved into two bands by the addition of 0.01% (v/v) dodecanol to the buffer. Protein extracted from the two bands obtained after electrophoresis of K. pneumoniae Mo-Fe protein gave unique and distinct peptide 'maps' after tryptic digestion. Undissociated Mo-Fe protein contained both sets of tryptic peptides. These data are consistent with Mo-Fe protein from K. pneumoniae being composed of non-identical subunits. Amino acid analyses of the subunit proteins revealed some clear differences in amino acid content, but the two subunits showed close compositional relatedness, with a different index [Metzer, H., Shapiro, M.B., Mosiman, J.E. & Vinton, J.G. (1968) Nature (London) 219, 1166-1168] of 4.7.
mesh_terms: D000596:Amino Acids / Q000032:analysis; D007501:Iron / Q000032:analysis; D007711:Klebsiella pneumoniae / Q000201:enzymology; D008667:Metalloproteins / Q000032:analysis*; D008982:Molybdenum / Q000032:analysis; D009591:Nitrogenase / Q000032:analysis*; D010446:Peptide Fragments / Q000032:analysis
chemical_list: D000596:Amino Acids; D008667:Metalloproteins; D010446:Peptide Fragments; D008982:Molybdenum; D007501:Iron; D009591:Nitrogenase