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'ATPase' in keywords Facet   Publication Year 1992  [X]
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1992[X]
1Author    Michaela Dane, Kerstin Steinert, Kordula Esser, Susanne Bickel-Sandkötter, Francisco Rodriguez-ValeraRequires cookie*
 Title    Properties of the Plasma Membrane ATPases of the Halophilic Archaebacteria Haloferax mediterranei and Haloferax volcanii  
 Abstract    Both, Haloferax mediterranei and Haloferax volcanii membranes contain ATPases which are capable of hydrolyzing ATP in presence of Mg2+ or M n2+. The ATPases require high con­ centrations of NaCl, a pH value of 9, and high temperatures up to 60 °C. Free manganese ions inhibited the enzyme activity of either ATPase. The ATPases of H f. mediterranei and H f. vol­ canii, respectively, show different sensitivities to inhibitors of ATP hydrolysis. ATP hydrolysis of isolated H f. mediterranei ATPase was inhibited by N aN 3, which was reported to be specific for F-ATPases, by nitrate and N-ethylmaleimide (NEM), which are specific inhibitors of V-ATPases. ATP hydrolysis of H aloferax mediterranei membranes was not inhibited by DCCD , but [14C]DCCD was bound to a 14 kDa peptide of the isolated, partially purified en­ zyme. Furthermore, the ATPase was inactivated by preincubation with 7-chloro-4-nitro-benzofurazan (NBD-C1). The ATPase activity of H f. volcanii membranes was inhibited by NEM but not by nitrate and N aN 3. SDS gel electrophoresis of the partially purified enzyme of Haloferax mediterranei showed putative ATPase subunits of 53. and 7.5 kDa. Immunoblots showed cross reactivity between a 53 kDa peptide and anti-$ (chloro­ plast F(), as well as between 53, 50 and 47 kDa peptides and an ATPase antibody of Methano-sarcina barkeri. The results will be discussed in context with the placement of the archaebac-terial ATPases (A-ATPases) between F-and V-ATPases. 
  Reference    Z. Naturforsch. 47c, 835—844 (1992); received June 29/September 10 1992 
  Published    1992 
  Keywords    Archaebacteria, Plasma Membrane, ATPase, Subunits, ATP Hydrolysis, Inhibition 
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 TEI-XML for    default:Reihe_C/47/ZNC-1992-47c-0835.pdf 
 Identifier    ZNC-1992-47c-0835 
 Volume    47 
2Author    ErwinW. BeckerRequires cookie*
 Title    Dynamics and Kinetics of Enzymes Kinetic Equilibrium of Forces in Biochemistry  
 Abstract    To explain the high specificity, high reaction rate, and high thermodynamic efficiency in enzymatic processes, cooperation of the enzyme with a molecular transfer unit is assumed. A "kinetic equilibrium of forces" is suggested, which enables high reaction rates to occur under equilibrium conditions and a thorough examination of the substrate to be made without con­ sumption of free energy. In case o f ATPases, ion-binding proteins are the most probable trans­ fer units. By analyzing the elementary effect in muscle contraction it is shown that the new theorem may be of substantial value in elucidating biochemical processes. 
  Reference    Z. Naturforsch. 47c, 628—633 (1992); received May 18 1992 
  Published    1992 
  Keywords    Enzyme, Mechanism, Free Energy Transfer, ATPase, Calmodulin, Muscle Contraction 
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 TEI-XML for    default:Reihe_C/47/ZNC-1992-47c-0628.pdf 
 Identifier    ZNC-1992-47c-0628 
 Volume    47