Characterization of molybdenum cofactor from Escherichia coli.

Published

Journal Article

Molybdenum cofactor activity was found in the soluble fraction of cell-free extracts of Escherichia coli grown aerobically in media supplemented with molybdate. Cofactor was detected by its ability to complement the nitrate reductase-deficient mutant of Neurospora crossa, nit-1, resulting in the vitro formation of nitrate reductase activity. Acid treatment of E. coli extracts was not required for release of cofactor activity. Cofactor was able to diffuse through a membrane of nominal 2,000-molecular-weight cutoff and was insensitive to trypsin. The cofactor was associated with a carrier molecule (approximately 40,000 daltons) during gel filtration and sucrose gradient centrifugation, but was easily removed from the carrier by dialysis. The carrier molecule protected the cofactor from inactivation by heat or oxygen. E. coli grown in molybdenum-free media, without and with tungsten, synthesized a metal-free "empty" cofactor and its tungsten analog, respectively, both of which were subsequently activated by the addition of molybdate. Empty and tungsten-containing cofactor complemented the nitrate reductase subunits in the nit-1 extract, forming inactive, but intact, 7.9S nitrate reductase. Addition of molybdate to the enzyme complemented in this manner restored nitrate reductase activity.

Full Text

Duke Authors

Cited Authors

  • Amy, NK; Rajagopalan, KV

Published Date

  • October 1, 1979

Published In

Volume / Issue

  • 140 / 1

Start / End Page

  • 114 - 124

PubMed ID

  • 387715

Pubmed Central ID

  • 387715

International Standard Serial Number (ISSN)

  • 0021-9193

Language

  • eng

Conference Location

  • United States