scholarly journals Molybdenum-independent nitrogenases of Azotobacter vinelandii: a functional species of alternative nitrogenase-3 isolated from a molybdenum-tolerant strain contains an iron-molybdenum cofactor

1993 ◽  
Vol 293 (1) ◽  
pp. 101-107 ◽  
Author(s):  
R N Pau ◽  
M E Eldridge ◽  
D J Lowe ◽  
L A Mitchenall ◽  
R R Eady
Keyword(s):  
Azotobacter Vinelandii ◽  
H2 Evolution ◽  
Titration Curves ◽  
Sds Page ◽  
Metal Requirement ◽  
Alternative Nitrogenase ◽  
Terminal Amino ◽  
Iron Molybdenum Cofactor ◽  
A New Species

Nitrogenase-3 of Azotobacter vinelandii is synthesized under conditions of molybdenum and vanadium deficiency. The minimal metal requirement for its synthesis, and its metal content, indicated that the only transition metal in nitrogenase-3 was iron [Chisnell, Premakumar and Bishop (1988) J. Bacteriol. 170, 27-33; Pau, Mitchenall and Robson (1989) J. Bacteriol. 171, 124-129]. A new species of nitrogenase-3 has been purified from a strain of A. vinelandii (RP306) lacking structural genes for the Mo- and V-nitrogenases and containing a mutation which enables nitrogenase-3 to be synthesized in the presence of molybdenum. SDS/PAGE showed that component 1 contained a 15 kDa polypeptide which N-terminal amino acid sequence determination showed to be encoded by anfG. This confirms that nitrogenase-3, like V-nitrogenase, comprises three subunits. Preparations of the nitrogenase-3 from strain RP306 contained 24 Fe atoms and 1 Mo atom per molecule. Characterization of the cofactor centre of the enzyme by e.p.r. spectroscopy and an enzymic cofactor assay, together with stimulation of the growth of strain RP306 by Mo, showed that nitrogenase-3 can incorporate the Mo-nitrogenase cofactor (FeMoco) to form a functional enzyme. The specific activities (nmol of product produced/min per mg of protein) determined from activity titration curves were: under N2, NH3 formation 110, with concomitant H2 evolution of 220; under argon, H2 evolution 350; under 10% acetylene (C2H2) in argon, ethylene (C2H4) 58, ethane (C2H6) 26, and concomitant H2 evolution 226. The rate of formation of C2H6 was non-linear, and the C2H6/C2H4 ratio strongly dependent on the ratio of nitrogenase components.

Characterization of Glycoprotein Fraction from Carp Pituitaries Isolated Using Concanavalin A as the Affinity Ligand

1998 ◽  
Vol 63 (3) ◽  
pp. 434-440 ◽  
Author(s):  
Irena Hulová ◽  
Jana Barthová ◽  
Helena Ryšlavá ◽  
Václav Kašička
Keyword(s):  
Concanavalin A ◽  
Reversed Phase ◽  
Amino Acid Sequences ◽  
Gel Chromatography ◽  
Affinity Ligand ◽  
Sds Page ◽  
Terminal Amino ◽  
Α And Β Subunits

Glycoproteins that have affinity to Concanavalin A were isolated from the acetone-dried pituitaries of common carp (Cyprinus carpio L.). Two fractions of glycoproteins were separated using gel chromatography on Superdex 75HR. The fraction with lower molecular weight (30 000) corresponding to the carp gonadotropin cGtH II was composed of two subunits as determined using SDS-PAGE. This protein fraction was further divided into four components using reversed-phase HPLC. Two fractions were pure α and β subunits of cGtH II as follows from immunodetection and from determination of N-terminal amino acid sequences. The other two were a mixture of α and β subunits as was also revealed by N-terminal analysis. Capillary electrophoresis was also used for characterization of isolated glycoproteins.

scholarly journals Purification and Characterization of NafY (Apodinitrogenase γ Subunit) fromAzotobacter vinelandii

2004 ◽  
Vol 279 (19) ◽  
pp. 19739-19746 ◽  
Author(s):  
Luis M. Rubio ◽  
Steven W. Singer ◽  
Paul W. Ludden
Keyword(s):  
Biochemical Characterization ◽  
Azotobacter Vinelandii ◽  
Site Directed Mutagenesis ◽  
Cofactor Binding ◽  
Unknown Structure ◽  
Additional Protein ◽  
Epr Signal ◽  
Iron Molybdenum Cofactor ◽  
Very High

The formation of an active dinitrogenase requires the synthesis and the insertion of the iron-molybdenum cofactor (FeMo-co) into a presynthesized apodinitrogenase. InAzotobacter vinelandii, NafY (also known as γ protein) has been proposed to be a FeMo-co insertase because of its ability to bind FeMo-co and apodinitrogenase. Here we report the purification and biochemical characterization of NafY and reach the following conclusions. First, NafY is a 26-kDa monomeric protein that binds one molecule of FeMo-co with very high affinity (Kd≈ 60 nm); second, the NafY-FeMo-co complex exhibits aS= 3/2 EPR signal with features similar to the signals for extracted FeMo-co and the M center of dinitrogenase; third, site-directed mutagenesis ofnafYindicates that the His121residue of NafY is involved in cofactor binding; and fourth, NafY binding to apodinitrogenase or to FeMo-co does not require the presence of any additional protein. In addition, we have obtained evidence that suggests the ability of NafY to bind NifB-co, an FeS cluster of unknown structure that is a biosynthetic precursor to FeMo-co.

Purification and characterization of a 4-hydroxybenzoate decarboxylase from an anaerobic coculture

2000 ◽  
Vol 46 (9) ◽  
pp. 856-859 ◽  
Author(s):  
Tong Li ◽  
Pierre Juteau ◽  
Réjean Beaudet ◽  
François Lépine ◽  
Richard Villemur ◽  
...  
Keyword(s):  
Gel Chromatography ◽  
Enterobacter Agglomerans ◽  
Anaerobic Conditions ◽  
Purification And Characterization ◽  
Terminal Amino Acid ◽  
Cell Extracts ◽  
Sds Page ◽  
Oxygen Sensitive ◽  
Terminal Amino

The oxygen-sensitive 4-hydroxybenzoate decarboxylase (4OHB-DC) activity from a phenol-carboxylating coculture, consisting of Clostridium-like strain 6 and an unidentified strain 7, was studied. Assays done with cell extracts showed that the optimal pH was 5.0-6.5 and the Kmwas 5.4 mM. The activity decreased by 50% in the presence of 5 mM EDTA, and it was restored and even enhanced by the addition of Mg++, Mn++, Zn++, or Ca++. After purification, the molecular mass of the enzyme was estimated as 420 kDa by gel chromatography, and as 119 kDa by SDS-PAGE, suggesting a homotetrameric structure. Its pI was 5.6. The N-terminal amino acid sequence showed 95% and 76% homology with the pyruvate-flavodoxin oxidoreductase (nifJ gene product) from Enterobacter agglomerans and Klebsiella pneumoniae, respectively. The purified enzyme also slowly catalyzed the reverse reaction, that is the phenol carboxylation. These characteristics suggest that this enzyme is different from other known decarboxylases. This includes the 4OHB-DC from Clostridium hydroxybenzoicum, which is the only one that had been purified before.Key words: purification, 4-hydroxybenzoate decarboxylase, coculture, phenol carboxylation, anaerobic conditions.

scholarly journals Flavodoxin 1 of Azotobacter vinelandii: characterization and role in electron donation to purified assimilatory nitrate reductase

1996 ◽  
Vol 317 (1) ◽  
pp. 103-108 ◽  
Author(s):  
Rathi GANGESWARAN ◽  
Robert R. EADY
Keyword(s):  
Nitrate Reductase ◽  
Electron Donor ◽  
Electrospray Mass Spectrometry ◽  
31P Nmr ◽  
Azotobacter Vinelandii ◽  
Redox Couples ◽  
Related Organism ◽  
Sds Page ◽  
Terminal Amino ◽  
Electron Donation

Flavodoxins synthesized by Azotobacter vinelandii strain UW 136 during growth on nitrate as nitrogen source were separated by FPLC on a Mono Q column into two species, flavodoxin 1 (AvFld 1) and flavodoxin 2 (AvFld 2). Both proteins migrated as single bands on SDS/PAGE. AvFld 1 was approx. 5-fold more abundant than AvFld 2 in the unresolved flavodoxin mixture. N-terminal amino acid analysis showed the sequence of AvFld 2 to correspond to the nif F gene product, an electron donor to nitrogenase. The sequences also show that these species corresponded to the flavodoxins Fld A and Fld B isolated from N2-grown cultures of the closely related organism Azotobacter chroococcum [Bagby, Barker, Hill, Eady and Thorneley (1991) Biochem. J. 277, 313–319]. Electrospray mass spectrometry gave Mr values for the polypeptides of 19430±3 and 19533±5 respectively. 31P-NMR measurements showed that in addition to the phosphate associated with the FMN (Δ = -136.3 p.p.m. and -135.48 p.p.m.), AvFld 1 had a signal at Δ = -142.1 p.p.m. and AvFld 2 at Δ = -138.59 p.p.m. present in substoichiometric amounts with FMN. These appeared to arise from unstable species since they were readily lost on further manipulation of the proteins. The mid-point potentials of the semiquinone–hydroquinone redox couples were -330 mV and -493 mV for AvFld 1 and AvFld 2 respectively, but only AvFld 1 was competent in donating electrons to the purified assimilatory nitrate reductase of A. vinelandii to catalyse the reduction of nitrate to nitrite. Flavodoxin isolated from NH4+-grown cells (Fld 3) also functioned as electron donor at half the rate of AvFld 1, but ferredoxin 1 from A. chroococcum did not.

Electrochemical characterization of the iron-molybdenum cofactor from Azotobacter vinelandii nitrogenase

1985 ◽  
Vol 107 (19) ◽  
pp. 5364-5368 ◽  
Author(s):  
Franklin A. Schultz ◽  
Stephen F. Gheller ◽  
Barbara K. Burgess ◽  
Samuel Lough ◽  
William E. Newton
Keyword(s):  
Azotobacter Vinelandii ◽  
Molybdenum Cofactor ◽  
Electrochemical Characterization ◽  
Iron Molybdenum Cofactor

Characterization of transcripts expressed from nitrogenase-3 structural genes of Azotobacter vinelandii

1992 ◽  
Vol 38 (9) ◽  
pp. 929-936 ◽  
Author(s):  
R. Premakumar ◽  
Marty R. Jacobson ◽  
Telisa M. Loveless ◽  
Paul E. Bishop
Keyword(s):  
Azotobacter Vinelandii ◽  
Coding Region ◽  
Base Pairs ◽  
S1 Nuclease ◽  
Mrna Species ◽  
Mutant Strains ◽  
S1 Nuclease Mapping ◽  
Alternative Nitrogenase ◽  
Nuclease Mapping

Five major anfH-hybridizing mRNA species accumulated in Azotobacter vinelandii cells derepressed for nitrogenase-3 (an alternative nitrogenase, which appears to lack Mo and V). Using anfH-, anfD-, anfG-, anfK-, and orf1orf2-specific probes and mutant strains of A. vinelandii these mRNA species have been identified as encoding anfHDGKorf1orf2 (6.0 kb), anfHDGK (4.3 kb), anfHD (2.6 kb), vnfHorfFd (1.3 kb), and vnfH and (or) anfH(1.0 kb). A 0.6-kb mRNA species, which hybridized only to the orf1orf2-specific probe, and a 3.5-kb mRNA species, which hybridized to anfD or anfK, also accumulated under these conditions. Northern blot analysis and S1 nuclease mapping indicate that transcription of the anf structural gene cluster initiates at a unique nif consensus promoter situated 127 base pairs upstream from the anfH coding region. Observation of anfH-hybridizing mRNA species that accumulate in strains derepressed for nitrogen fixation demonstrates that transcription of the anfHDGKorf1orf2 cluster is normally repressed by Mo, V, and NH4+, whereas transcription of the vnfHorfFd cluster does not require the presence of V and is repressed only by Mo, but not NH4+. Analysis of the accumulation of mRNAs in a tungsten-tolerant strain revealed that Mo and V repression of anf transcription must occur by different mechanisms. Key words: Azotobacter vinelandii, nitrogenase-3, transcripts, regulation, molybdenum, vanadium.

Isolation, purification and characterization of chymosin from riverine buffalo (Bubalos bubalis)

2003 ◽  
Vol 70 (1) ◽  
pp. 37-43 ◽  
Author(s):  
Ashok K Mohanty ◽  
Utpal K Mukhopadhyay ◽  
Jai K Kaushik ◽  
Sunita Grover ◽  
Virender K Batish
Keyword(s):  
Amino Acid ◽  
Proteolytic Activity ◽  
Gel Filtration ◽  
Maximum Activity ◽  
Amino Acid Sequences ◽  
Milk Clotting ◽  
Sds Page ◽  
Terminal Amino ◽  
The Stability

Chymosin, an aspartyl proteinase, is used for curdling of milk and manufacture of cheese. We report the purification and the physicochemical properties of chymosin isolated from the abomasal tissue of buffalo calves. The enzyme preparation extracted from buffalo abomasal tissues could be purified 29–fold using anion exchange and gel filtration chromatography. The molecular weight of the purified enzyme was 35·6 kDa on SDS-PAGE. Partial N-terminal amino acid sequence of the first eight amino acid sequences of buffalo chymosin was identical to the first eight amino acid sequences of cattle chymosin. Buffalo chymosin exhibited a skewed bell-shaped stability profile as a function of temperature with maximum activity near 55 °C. Milk clotting activity decreased gradually as pH increased. The enzyme became completely inactive, however, above pH 7·0. The ratio of milk clotting to proteolytic activity was 3·03. When compared with cattle chymosin, there were subtle differences in the stability and relative proteolytic activity of buffalo chymosin.

The Immuno-Electron Microscopic Localization of the Mo-Fe Protein Component of Nitrogenase in Cells of Azotobacter Vinelandii

1973 ◽  
Vol 31 ◽  
pp. 574-575
Author(s):  
J. T. Stasny ◽  
R. C. Burns ◽  
R. W. F. Hardy
Keyword(s):  
Cellular Localization ◽  
Direct Evidence ◽  
Azotobacter Vinelandii ◽  
Intracellular Localization ◽  
Protein Component ◽  
Electron Microscopic ◽  
Thin Sections ◽  
Fe Protein ◽  
Intracytoplasmic Membranes

Structure-functlon studies of biological N2-fixation have correlated the presence of the enzyme nitrogenase with increased numbers of intracytoplasmic membranes in Azotobacter. However no direct evidence has been provided for the internal cellular localization of any nitrogenase. Recent advances concerned with the crystallizatiorTand the electron microscopic characterization of the Mo-Fe protein component of Azotobacter nitrogenase, prompted the use of this purified protein to obtain antibodies (Ab) to be conjugated to electron dense markers for the intracellular localization of the protein by electron microscopy. The present study describes the use of ferritin conjugated to goat antitMo-Fe protein immunoglobulin (IgG) and the observations following its topical application to thin sections of N2-grown Azotobacter.

PURIFICATION AND PARTIAL CHEMICAL CHARACTERIZATION OF SHEEP NEUROPHYSIN

1973 ◽  
Vol 74 (2) ◽  
pp. 226-236 ◽  
Author(s):  
Michel Chrétien ◽  
Claude Gilardeau
Keyword(s):  
Amino Acid ◽  
Polyacrylamide Gel Electrophoresis ◽  
Chemical Characterization ◽  
Terminal Amino Acid ◽  
Amino Acid Determination ◽  
Pituitary Glands ◽  
Terminal Amino ◽  
Partial Chemical ◽  
Acid Determination

ABSTRACT A protein isolated from ovine pituitary glands has been purified, and its homogeneity assessed by NH2- and COOH-terminal amino acid determination, ultracentrifugation studies, and polyacrylamide gel electrophoresis after carboxymethylation. Its chemical and immunochemical properties are closely similar to those of beef and pork neurophysins, less similar to those of human neurophysins. It contains no tryptophan (like other neurophysins) or histidine (like all except bovine neurophysin-I and human neurophysins). It has alanine at the NH2-terminus and valine at the COOH-terminus. Its amino acid composition is similar to, but not identical with those of porcine and bovine neurophysins.

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