Open AccessRegulation of the mdh‐sucCDAB operon in Rhizobium leguminosarum
Author(s) -
Poole Philip,
Reid Colm,
East Alison K.,
Allaway David,
Day Michael,
Leonard Mary
Publication year - 1999
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.1999.tb13669.x
Subject(s) - malate dehydrogenase , homotetramer , biology , operon , rhizobium leguminosarum , biochemistry , dehydrogenase , complementation , microbiology and biotechnology , structural gene , gene , rhizobiaceae , enzyme , mutant , genetics , bacteria , symbiosis , protein subunit
The malate dehydrogenase gene, mdh , from Rhizobium leguminosarum encodes a protein with a molecular weight of 33 590 that associates as a homotetramer. It is a lactate dehydrogenase‐like malate dehydrogenase that most closely resembles the protein from the colonial green alga Botryococcus braunii . Malate dehydrogenase from R. leguminosarum has a K m of 74 μM and a V max of 822 μmol min −1 mg −1 protein for oxaloacetate, while the K m for malate is 3.6 mM and the V max 62 μmol min −1 mg −1 protein. Downstream of mdh are sucCDAB , which encode succinyl‐CoA synthetase ( sucCD ) and the E1 and E2 components of the α‐ketoglutarate dehydrogenase complex ( sucAB ). Complementation and LacZ fusion analysis indicates that there is a common promoter for the mdh‐suc genes. Mutation of downstream genes in the mdh‐suc operon increases transcription 7‐fold from the mdh promoter. The transcriptional coupling of mdh and sucCDAB is likely to be important in the regulation of carbon and nitrogen metabolism in bacteroids.