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Properties of seleno-methionine substituted assimilatory nitrate reductase

Conference · · FASEB Journal (Federation of American Societies for Experimental Biology); (United States)
OSTI ID:5373095
;  [1]
  1. Univ. of South Florida, Tampa (United States)
Assimilatory NADH:nitrate reductase contains FAD, heme and Mo-pterin arranged in an NADH{yields}FAD{yields}heme{yields}Mo-Pterin{yields}NO{sub 3} electron transfer sequence. A functional Mo-pterin center is essential for all nitrate-reducing activities. To assess the possible functional role of Met, a Se-Met substituted NR was obtained by addition of Se-Met to ammonia-grown Chlorella cells prior to induction of NR activity. Increase in NADH:dehydrogenase partial activities and nitrate reductase protein proceeded normally following induction but little or no nitrate-reducing activity was expressed. This effect was observed with as little as 10{sup {minus}5} Se-Met and was prevented by a 10-fold excess of Met. A less pronounced effect was observed with 10{sup {minus}4}M Se-Cys. The purified Se-Met substituted enzyme exhibited the same apparent physical size, spectral properties and NADH dehydrogenase activities as control NR but was devoid of nitrate-reducing activities. These results suggest that one or more Met residues are essential for the catalytic function of the molybdo-pterin center of assimilatory NR.
OSTI ID:
5373095
Report Number(s):
CONF-9104107--
Conference Information:
Journal Name: FASEB Journal (Federation of American Societies for Experimental Biology); (United States) Journal Volume: 5:4
Country of Publication:
United States
Language:
English