Electron transport systems of Rhizobium japonicum. II. Rhizobium haemoglobin, cytochromes and oxidases in free-living (cultured) cells

1969 ◽  
Vol 172 (1) ◽  
pp. 88-105 ◽  
Author(s):  
C.A. Appleby
Keyword(s):  
Electron Transport ◽  
Cultured Cells ◽  
Transport Systems ◽  
Rhizobium Japonicum ◽  
Free Living

Electron transport components involved in hydrogen oxidation in free-living Rhizobium japonicum

1982 ◽  
Vol 152 (1) ◽  
pp. 422-430
Author(s):  
M R O'Brian ◽  
R J Maier
Keyword(s):  
Electron Transport ◽  
Hydrogen Oxidation ◽  
Uv Light ◽  
Absorption Peak ◽  
Rhizobium Japonicum ◽  
O2 Uptake ◽  
Difference Spectra ◽  
Transport Pathway ◽  
Free Living ◽  
H2 Oxidation

Membranes from free-living Rhizobium japonicum were isolated to study electron transport components involved in H2 oxidation. The H2/O2 uptake rate ratio in membranes was approximately 2. The electron transport inhibitors antimycin A, cyanide, azide, hydroxylamine, and 2-n-heptyl-4-hydroxyquinoline-N-oxide (HQNO) inhibited H2 uptake and H2-dependent O2 uptake significantly. H2-reduced minus O2-oxidized absorption difference spectra revealed peaks at 551.5, 560, and 603 nm, indicating the involvement of cytochromes c, b, and a-a3, respectively. H2-dependent cytochrome reduction was completely inhibited in the presence of 0.15 mM HQNO. This inhibition was relieved by the addition of 0.1 mM menadione. Evidence is presented for the involvement of two b-type cytochromes in H2 oxidation. One b-type cytochrome was not reduced by ascorbate and had an absorption peak at 560 nm. The reduction of this cytochrome by H2 was not inhibited by cyanide. A second b-type cytochrome, cytochrome b', was not reduced by H2 in the presence of cyanide. This cytochrome had an absorption peak at 558 nm. Carbon monoxide difference spectra with H2 as reductant provided evidence for the involvement of cytochrome o as well as cytochrome a3 in H2 oxidation. H2 uptake activity in cell-free extracts was inhibited by UV light irradiation. Most of the activity of the UV-treated extracts was restored with the addition of ubiquinone. The restored activity was inhibited by cyanide. A branched electron transport pathway from H2 to O2 is proposed.

Comparative studies on succinate and terminal oxidase activity in microbial and mammalian electron-transport systems

1969 ◽  
Vol 15 (7) ◽  
pp. 797-807 ◽  
Author(s):  
Peter Jurtshuk ◽  
Ann K. May ◽  
Leodocia M. Pope ◽  
Patricia R. Aston
Keyword(s):  
Electron Transport ◽  
Cytochrome C ◽  
Comparative Studies ◽  
Azotobacter Vinelandii ◽  
Transport Systems ◽  
Terminal Oxidase ◽  
Succinate Oxidation ◽  
State Reduction ◽  
Hydroxy Quinoline ◽  
Terminal Oxidation

A comparative study was undertaken to examine the succinate and terminal oxidase activities of the electron-transport systems of Azotobacter vinelandii and mammalian mitochondria. For succinate oxidation, both systems exhibited similar relative specificities for the electron acceptors phenazine methosulfate, O2, methylene blue, K3Fe(CN)6, nitrotetrazolium blue, 2,6-dichlorophenolindophenol (DCIP), and cytochrome c. They differed in that DCIP and cytochrome c were less active in the Azotobacter electron-transport system (R3 fraction) than in the bovine mitochondrial system. Comparative studies with known inhibitors of mammalian mitochondrial electron-transport demonstrated that the succinoxidase activity of the Azotobacter R3 fraction was, at least, 2000 times less sensitive to antimycin A, 700 times less sensitive to thenoyl-trifluoroacetone, and 30 times less sensitive to 2-n-heptyl-4-hydroxy-quinoline-N-oxide. Both systems were equally sensitive to KCN, p-chloromercuribenzoic acid, and chlorpromazine.The ability of the two systems to use tetramethyl-p-phenylenediamine (TMPD) and its derivatives as electron donors, for terminal oxidation, was also similar. Studies on steady state reduction revealed that in the Azotobacter R3 fraction, the cytochromes (a2, a1, b1, c4 + c5) and flavoprotein components were reduced substantially by succinate as well as by TMPD in the presence of ascorbate. Ultrastructure analyses of the Azotobacter R3 electron-transport fraction revealed the vesicular membranous components identified as oxidosomes according to the terminology used by DeLey and contained spherical headpiece units of 80 Å in diameter which appeared to be morphologically identical with the tripartite units or the elementary particles described by Green and associates, viz., Kopaczyk et al., and by Fernandez-Moran et al.

scholarly journals Effect of serum proteins on sodium-linked transport processes in cultured kidney cells.

1995 ◽  
Vol 5 (11) ◽  
pp. 1964-1970
Author(s):  
S S Blumenthal ◽  
D L Lewand ◽  
P A Tipnis ◽  
J G Kleinman
Keyword(s):  
Amino Acid ◽  
Dextran Sulfate ◽  
Cultured Cells ◽  
Serum Proteins ◽  
Fluid Phase ◽  
Defined Medium ◽  
Transport Processes ◽  
Transport Systems ◽  
Heat Treated ◽  
Fluid Phase Endocytosis

The mechanism for increased Na+ retention in the nephrotic syndrome is unknown. To determine if Na+ transport systems in the proximal tubule might be affected by filtered proteins, mouse cortical tubule cells grown in defined medium were exposed to concentrations of bovine serum albumin (BSA) ranging from 0.01 to 0.5%. Activity of the Na(+)-glucose cotransporter, measured as Na(+)-dependent uptake of alpha-methylglucoside, increased progressively to a maximum of 2.3-fold above baseline (P < 0.001; N = 10). The increase in transporter activity was due to an increased Vmax, and the magnitude of the increase was inversely related to the basal cotransporter activity of the cultures. Increased cotransporter activity was detectable 6 h after exposure, was sustained for 24 h after cells were removed from an albumin-free medium, and was prevented by cycloheximide. Heat-treated BSA, fatty-acid and globulin-free BSA, and gamma-globulins were as effective at increasing Na(+)-glucose cotransporter activity as untreated Fraction V BSA. Dextran, dextran-sulfate, and amino acid supplements were ineffective. Neither protease inhibitors nor chloroquine added to an albumin-containing medium prevented increased alpha-methylglucoside uptake. Albumin did not change the rate of fluid-phase endocytosis in the cultured cells. Na(+)-amino acid cotransport and Na(+)-H+ exchange were either decreased or unchanged after BSA exposure. Exposing apical surfaces of cells grown on permeable membranes to BSA led to a greater increase in activity of the Na(+)-glucose cotransporter relative to controls than did exposing the basolateral surface (145 versus 89%; P < 0.05; N = 5).(ABSTRACT TRUNCATED AT 250 WORDS)

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