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  • Hydrogenase apoprotein  (1)
  • Lagrangian manifold  (1)
  • Rhizobium japonicum, CO2 fixation  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Nickel-dependent reconstitution of hydrogenase apoprotein in Bradyrhizobium japonicum Hupc mutants and direct evidence for a nickel metabolism locus involved in nickel incorporation into the enzyme (1992)
    Springer
    Archives of microbiology 157 (1992), S. 493-498 
    Details
    ISSN: 1432-072X
    Keywords: Bradyrhizobium japonicum ; Hupc mutants ; Hydrogenase apoprotein ; Nickel metabolism ; Nickel incorporation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A double mutant (JH103K10) was created from hydrogenase constitutive mutant (JH103) by replacement of a chromosomal 0.60 kb nickel metabolism related locus with a kanamycin resistance gene. The double mutant required 10 to 20 times more nickel (Ni) to achieve near parental strain levels of hydrogenase activity. In the absence of nickel, both JH103K10 and JH103 synthesized high levels of (inactive) hydrogenase apoprotein (large subunit, 65 kDa). With nickel, the double mutant JH103K10 synthesized the same level of hydrogenase apoenzyme (65-kDa subunit) as the JH103 parent strain; however, whole cell hydrogenase activity in JH103K10 was less than half of that in JH103, and the CPM (due to 63Ni in hydrogenase) of membranes and the calculated ratio of nickel per unit of hydrogenase enzyme of the double mutant were 40% of that in JH103. Therefore, the difference in hydrogenase activities between the double mutant and the Hupck strain can be accounted for by different abilities of the strains to incorporate nickel into the hydrogenase apoenzyme. The addition of nickel ions to previously Ni-starved and then chloramphenicol-treated Bradyrhizobium japonicum whole cells (JH103 and JH103K10) resulted in (an in vivo) restoration of hydrogenase activity, suggesting that the apoprotein synthesized in the Ni-free cultures could be activated by addition of nickel even in the absence of protein synthesis. The extent of reconstitution of active hydrogenase by nickel was greater in the absence of chloramphenicol. Hydrogenase apoprotein could not be activated by nickel in vitro even with the addition of ATP. The successful in vivo but not in vitro results suggest that enzymatic but cell-disruption labile factors are required for Ni incorporation into hydrogenase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00276768
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  • 2
    Electronic Resource
    Electronic Resource
    Hydrogen-stimulated CO2 fixation and coordinate induction of hydrogenase and ribulosebiphosphate carboxylase in a H2-uptake positive strain of Rhizobium japonicum (1979)
    Springer
    Archives of microbiology 123 (1979), S. 1-8 
    Details
    ISSN: 1432-072X
    Keywords: Hydrogenase ; Ribulosebisphosphate carboxylase ; Hydrogen uptake ; Rhizobium japonicum, CO2 fixation ; Propionyl coenzyme A carboxylase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract H2-uptake positive strains (122 DES and SR) and H2-uptake negative strains SR2 and SR3 of Rhizobium japonicum were examined for ribulosebisphosphate (RuBP) carboxylase and H2-uptake activities during growth conditions which induced formation of the hydrogenase system. The rate of 14CO2 uptake by hydrogenase-derepressed cells was about 6-times greater in the presence than in the absence of H2. RuBP carboxylase activity was observed in free-living R. japonicum strains 122 DES or SR only when the cells were derepressed for their hydrogenase system. Hydrogenase and RuBP carboxylase activities were coordinately induced by H2 and both were repressed by added succinate. Hydrogenase-negative mutant strains SR2 and SR3 derived from R. japonicum SR showed no detecyable RuBP carboxylase activities under hydrogenase derepression conditions. No detectable RuBP carboxylase was observed in bacteroids formed by H2-uptake positive strains R. japonicum 122 DES or SR. Propionyl CoA carboxylase activity was consistently observed in extracts of cells from free-living cultures of R. japonicum but activity was not appreciably influenced by the addition of H2. Neither phosphoenolpyruvate carboxylase nor phosphoenolpyruvate carboxykinase activity was detected in extracts of R. japonicum.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00403496
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  • 3
    Electronic Resource
    Electronic Resource
    A scaling theory of bifurcations in the symmetric weak-noise escape problem (1996)
    Springer
    Journal of statistical physics 83 (1996), S. 291-357 
    Details
    ISSN: 1572-9613
    Keywords: Boundary layer ; caustics ; double well ; Fokker-Planck equation ; Lagrangian manifold ; large deviation theory ; large fluctuations ; Maslov-WKB method ; non-Arrhenius behavior ; nongeneric caustics ; Pearcey function ; singular perturbation theory ; Smoluchowski equation ; stochastic escape problem ; stochastic exit problem ; stochastically perturbed dynamical systems ; weak noise ; Wentzell-Freidlin theory ; WKB approximation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We consider two-dimensional overdamped double-well systems perturbed by white noise. In the weak-noise limit the most probable fluctuational path leading from either point attractor to the separatrix (the most probable escape path, or MPEP) must terminate on the saddle between the two wells. However, as the parameters of a symmetric double-well system are varied, a unique MPEP may bifurcate into two equally likely MPEPs. At the bifurcation point in parameter space, the activation kinetics of the system become non-Arrhenius. We quantify the non-Arrhenius behavior of a system at the bifurcation point, by using the Maslov-WKB method to construct an approximation to the quasistationary probability distribution of the system that is valid in a boundary layer near the separatrix. The approximation is a formal asymptotic solution of the Smoluchowski equation. Our construction relies on a new scaling theory, which yields “critical exponents” describing weak-noise behavior at the bifurcation point, near the saddle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02183736
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    Paper (German National Licenses)
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