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1987 (1)
1986 (1)
1Author    Ruth Hracky, Jürgen SollRequires cookie*
 Title    Protein Phosphorylation — Dephosphorylation in the Cytosol of Pea Mesophyll Cells  
 Abstract    Soluble protein kinase and protein phosphatase activities were localized in the cytosol of pea mesophyll cells using protoplasts fractionation techniques. The molecular weights of the phos-phorylated cytosolic proteins, as determined by polyacrylamide gel electrophoresis, were 68, 55, 46, 38, 36, 30, 22 and 12 kDa. Histone and, to a much lesser extent, casein but not phosvitin were accepted as exogenous substrates. In every case serine served as acceptor amino acid for the phosphate residue. The protein phosphorylation activity had an alkaline pH optimum, and showed no response to varying Mg2+, Ca2+, Pn cyclo-AMP or calmodulin concentrations. The kinase activity was competitively inhibited by ADP and pyrophosphate with apparent K t values of 0.5 and 0.17 m M , respectively. High ATP concentrations (1 -4 m M) resulted in a strong decrease of radioactivity in the ,2P labeled proteins. It is proposed that the ratio of protein phosphorylation to protein dephosphorylation is regulated by the ATP to ADP ratio in the cytosol. 
  Reference    Z. Naturforsch. 41c, 856 (1986); received July 9/August 5 1986 
  Published    1986 
  Keywords    Protein Kinase, Protein Phosphatase, Cytosol, Protoplasts, Pisum sativum 
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 TEI-XML for    default:Reihe_C/41/ZNC-1986-41c-0856.pdf 
 Identifier    ZNC-1986-41c-0856 
 Volume    41 
2Author    G. Ünter Müller, W. Olfhard BandlowRequires cookie*
 Title    cA M P-Dependent Protein Kinase Activity in Yeast Mitochondria  
 Abstract    Two different cAMP-binding proteins have been identified in yeast mitochondria by photo­ affinity labelling and based on the occurrence of cAMP-binding activity in two different sub-mito­ chondrial fractions. One protein (M r 45—46000) is tightly bound to the inner mitochondrial membrane whereas the other (M r 42000) is found in the soluble intermembrane space. With endogenous substrate cAMP-dependent protein kinase activity could not be demonstrated with sufficient clarity. However, using acidic heterologous substrates, like casein and phosvitin, one cAMP-dependent protein kinase was identified in the intermembrane space. Only low phosphate incorporation was found using histone fractions as substrate. cAMP-dependent modification of proteins appears to be very shortlived in mitochondria. Its physiological significance remains unknown, since neither mitochondrial transcription, translation, respiration nor import of cyto-plasmically synthesized precursors into mitochondria appear to be influenced by exogenous cAMP either in vivo or in vitro. It is shown that cAMP is not actively transported into the inner mitochondrial compartment but rather binds to a receptor(s) localized outside the permeability barrier provided by the inner membrane. 
  Reference    Z. Naturforsch. 42c, 1291 (1987); received May 29/August 3. 1987 
  Published    1987 
  Keywords    cAMP-Dependent Protein Kinase, Protein Phosphatase, Yeast, Mitochondria, Sub-Mitochon-drial Location 
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 TEI-XML for    default:Reihe_C/42/ZNC-1987-42c-1291.pdf 
 Identifier    ZNC-1987-42c-1291 
 Volume    42