{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,12]],"date-time":"2025-10-12T19:59:51Z","timestamp":1760299191255},"reference-count":0,"publisher":"Portland Press Ltd.","issue":"3","content-domain":{"domain":["portlandpress.com"],"crossmark-restriction":true},"short-container-title":[],"published-print":{"date-parts":[[1984,11,1]]},"abstract":"<jats:p>The inactive MoFe protein (NifB-Kp1) of nitrogenase from nifB mutants of Klebsiella pneumoniae may be activated by addition of the iron-molybdenum cofactor (FeMoco) extracted from active MoFe protein (Kp1). However, when apparently saturated with FeMoco, our preparations of NifB-Kp1 yielded activated protein, Kp1-asm, with a specific activity that was at best only 40% of that expected. This was not due to degradation of Kp1-asm, NifB-Kp1 or FeMoco during the activation reaction. Nor could activation be enhanced by addition of other nif-gene products or other proteins. Whereas fully active Kp1 contains 2 FeMoco\/molecule, apparent saturation of our NifB-Kp1 preparations required the binding of only 0.4-0.65 FeMoco\/molecule. By using chromatography Kp1-asm could be largely resolved from NifB-Kp1 that had not been activated. However, we were unable to isolate fully active MoFe protein (i.e. Kp1-asm containing 2 FeMoco\/molecule) from solutions of NifB-Kp1 activated with FeMoco. The maximum activity\/ng-atom of total Mo obtained for our purified Kp1-asm was approximately half the maximum activity for FeMoco. Since all NifB-Kp1 preparations contained some Mo, we suggest that FeMoco activated only those NifB-Kp1 molecules already containing one atom of (non-FeMoco) Mo, thus forming Kp1-asm with 2 Mo but only 1 FeMoco\/molecule. Kp1-asm was identical with normal Kp1 in terms of its Mr, stability, e.p.r. signals, pattern of substrate reductions, CO inhibition and ATP\/2e ratio. In addition, for preparations of differing specific activity, there was a constant and identical relationship between the e.p.r. signal intensity (from FeMoco) and the activity of both Kp1 and Kp1-asm. Assuming the above hypothesis on the structure of Kp1-asm, these data demonstrate that the two FeMoco sites in wild-type Kp1 operate independently.<\/jats:p>","DOI":"10.1042\/bj2230783","type":"journal-article","created":{"date-parts":[[2015,8,10]],"date-time":"2015-08-10T20:46:01Z","timestamp":1439239561000},"page":"783-792","update-policy":"http:\/\/dx.doi.org\/10.1042\/crossmark_policy","source":"Crossref","is-referenced-by-count":21,"title":["The inactive MoFe protein (NifB\u2212Kp1) of the nitrogenase from <i>nif B<\/i> mutants of <i>Klebsiella pneumoniae<\/i>. Its interaction with FeMo-cofactor and the properties of the active MoFe protein formed"],"prefix":"10.1042","volume":"223","author":[{"given":"T R","family":"Hawkes","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"B E","family":"Smith","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"288","container-title":["Biochemical Journal"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/portlandpress.com\/biochemj\/article-pdf\/223\/3\/783\/633585\/bj2230783.pdf","content-type":"application\/pdf","content-version":"vor","intended-application":"syndication"},{"URL":"https:\/\/portlandpress.com\/biochemj\/article-pdf\/223\/3\/783\/633585\/bj2230783.pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2021,11,25]],"date-time":"2021-11-25T14:44:49Z","timestamp":1637851489000},"score":1,"resource":{"primary":{"URL":"https:\/\/portlandpress.com\/biochemj\/article\/223\/3\/783\/19151\/The-inactive-MoFe-protein-NifB-Kp1-of-the"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[1984,11,1]]},"references-count":0,"journal-issue":{"issue":"3","published-print":{"date-parts":[[1984,11,1]]}},"URL":"https:\/\/doi.org\/10.1042\/bj2230783","relation":{},"ISSN":["0264-6021","1470-8728"],"issn-type":[{"value":"0264-6021","type":"print"},{"value":"1470-8728","type":"electronic"}],"subject":[],"published":{"date-parts":[[1984,11,1]]}}}