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Purification and properties of mercuric reductase from Azotobacter chroococcum
, P C SADHUKHAN, J CHAUDHURI, D K GHOSH, A MANDAL
Published in BLACKWELL SCIENCE LTD
1999
Volume: 86
   
Issue: 1
Pages: 7 - 12
Abstract
Mercury resistance determinants in bacteria are often plasmid-borne or transposon-mediated. Mercuric reductase, one of the proteins encoded by the mercury resistance operon, catalyses a unique reaction in which mercuric ions, Hg (II), are reduced to mercury metal Hg(O) using NADPH as a source of reducing power. Mercuric reductase was purified from Azotobacter chroococcum SS2 using Red A dye matrix affinity chromatography. Freshly purified preparations of the enzyme showed a single band on polyacrylamide gel electrophoresis under non-denaturing conditions. After SDS-polyacrylamide gel electrophoresis of the freshly prepared enzyme, two protein bands, a major and a minor one, were observed with molecular weight 69 000 and 54 000, respectively. The molecular weight of the native enzyme as determined by gel filtration in Sephacryl S-300 was 142 000. The Km of Hg2+-reductase for HgCl2 was 11.11 μmol l-1. Titration with 5,5'-dithiobis (2- nitrobenzoate) demonstrated that two enzyme-SH groups become kinetically accessible on reduction with NADPH.
About the journal
JournalJournal of Applied Microbiology
PublisherBLACKWELL SCIENCE LTD
ISSN1364-5072
Open AccessNo