title: Identification and Characterization of a Bacteroid-Specific Dehydrogenase Complex in Rhizobium leguminosarum PRE.
abstract: In membranes of Rhizobium leguminosarum bacteroids isolated from nitrogen-fixing pea root nodules, two different protein complexes with NADH dehydrogenase activity were detected. One of these complexes, with a molecular mass of 110 kilodaltons, was also found in membranes of free-living rhizobia, but the other, with a molecular mass of 550 kilodaltons, appeared to be present only in bacteroids. The bacteroid-specific complex, referred to as DH1, probably consists of at least four different subunits. Using antibodies raised against the separate polypeptides, we found that a 35,000-molecular-weight polypeptide (35K polypeptide) in the DH1 complex is bacteroid specific, while the other proposed subunits were also detectable in cytoplasmic membranes of free-living bacteria. Dehydrogenase complex DH1 is also present in bacteroids of a R. leguminosarum nifA mutant, indicating that the synthesis of the dehydrogenase is not dependent on the gene product of this nif-regulatory gene. A possible involvement of the bacteroid-specific DH1 complex in electron transport to nitrogenase is discussed.
authors.affiliation: Department of Molecular Biology, Agricultural University, DreijenLaan 3, 6703 HA Wageningen, The Netherlands.
authors.forename: R M
authors.initials: RM
authors.lastname: Lankhorst
authors.forename: P
authors.initials: P
authors.lastname: Katinakis
authors.forename: A
authors.initials: A
authors.lastname: van Kammen
authors.forename: R C
authors.initials: RC
authors.lastname: van den Bos