scholarly journals Purification and characterization of an oxygen-stable form of dinitrogenase reductase-activating glycohydrolase from Rhodospirillum rubrum

1994 ◽  
Vol 302 (3) ◽  
pp. 801-806 ◽  
Author(s):  
G M Nielsen ◽  
Y Bao ◽  
G P Roberts ◽  
P W Ludden
Keyword(s):  
Fluorescence Spectra ◽  
Rhodospirillum Rubrum ◽  
Sodium Dithionite ◽  
Stable Form ◽  
Purification And Characterization ◽  
Dinitrogenase Reductase ◽  
Bivalent Metals ◽  
Overexpressing Strain ◽  
Ribose Moiety

Dinitrogenase reductase-activating glycohydrolase (DRAG) is responsible for removing the ADP-ribose moiety from post-translationally inactivated nitrogenase of Rhodospirillum rubrum. Using DRAG purified from an overexpressing strain (UR276), further properties of this enzyme were studied, including its u.v.-visible and fluorescence spectra and its stability in air. DRAG appears to require no covalently bound inorganic cofactors for its activity or regulation. Previously, purified DRAG was found to be rapidly inactivated in air. The air-catalysed lability originated with the presence of sodium dithionite and Mn2+ throughout the purification of the enzyme. This lability can be mimicked using H2O2, which is known to oxidatively inactivate proteins containing bivalent metals. Implications for the regulation of nitrogenase are discussed with respect to the lack of sensitivity to air of the regulatory enzyme, DRAG.

scholarly journals Mutagenesis and Functional Characterization of theglnB, glnA, and nifA Genes from the Photosynthetic Bacterium Rhodospirillum rubrum

2000 ◽  
Vol 182 (4) ◽  
pp. 983-992 ◽  
Author(s):  
Yaoping Zhang ◽  
Edward L. Pohlmann ◽  
Paul W. Ludden ◽  
Gary P. Roberts
Keyword(s):  
Nitrogen Fixation ◽  
Rhodospirillum Rubrum ◽  
Nitrogenase Activity ◽  
Functional Characterization ◽  
Photosynthetic Bacterium ◽  
Wild Type ◽  
Adp Ribosylation ◽  
Dinitrogenase Reductase ◽  
Adp Ribosyltransferase

ABSTRACT Nitrogen fixation is tightly regulated in Rhodospirillum rubrum at two different levels: transcriptional regulation ofnif expression and posttranslational regulation of dinitrogenase reductase by reversible ADP-ribosylation catalyzed by the DRAT-DRAG (dinitrogenase reductase ADP-ribosyltransferase–dinitrogenase reductase-activating glycohydrolase) system. We report here the characterization ofglnB, glnA, and nifA mutants and studies of their relationship to the regulation of nitrogen fixation. Two mutants which affect glnB (structural gene for PII) were constructed. While PII-Y51F showed a lower nitrogenase activity than that of wild type, a PIIdeletion mutant showed very little nif expression. This effect of PII on nif expression is apparently the result of a requirement of PII for NifA activation, whose activity is regulated by NH4 + in R. rubrum. The modification of glutamine synthetase (GS) in theseglnB mutants appears to be similar to that seen in wild type, suggesting that a paralog of PII might exist inR. rubrum and regulate the modification of GS. PII also appears to be involved in the regulation of DRAT activity, since an altered response to NH4 + was found in a mutant expressing PII-Y51F. The adenylylation of GS plays no significant role in nif expression or the ADP-ribosylation of dinitrogenase reductase, since a mutant expressing GS-Y398F showed normal nitrogenase activity and normal modification of dinitrogenase reductase in response to NH4 + and darkness treatments.

Purification and characterization of glutathione reductase from Rhodospirillum rubrum

1992 ◽  
Vol 298 (1) ◽  
pp. 247-253 ◽  
Author(s):  
Carlos A. Libreros-Minotta ◽  
Juan P. Pardo ◽  
Guillermo Mendoza-Hernández ◽  
Juan L. Rendón
Keyword(s):  
Glutathione Reductase ◽  
Rhodospirillum Rubrum ◽  
Purification And Characterization
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