STIMULATED INCORPORATION OF AMINO ACIDS INTO PROTEINS OF SYNAPTOSOMAL FRACTIONS INDUCED BY DEPOLARIZING TREATMENTS |
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Authors: | E. Wedege Y. Luqmani H. F. Bradford |
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Affiliation: | Department of Biochemistry, Imperial College, London SW7 2AZ |
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Abstract: | Abstract— Rat cortical synaptosome preparations incorporated l -amino acids into protein at a linear rate over 30–60 min. Synaptosomes showed large increases in incorporation after treatment with electrical pulses, veratrine or K+. This was inhibited (controls, 73%; electrically stimulated 58%) by cycloheximide and by chloramphenicol (28 and 44% respectively). Omission of Ca2+ from the medium had no effect, but the absence of Na+ greatly diminished the stimulus-induced increase in incorporation due to pulses. Electrical pulses, veratrine and K+ (in order of effectiveness), all showed their greatest proportional effects on amino acid incorporation into the Triton-X-100 insoluble portions of the synaptosomal membrane: the 'junctional complex', soluble in SDS, and the residue. Tetrodotoxin (1 μ m ), although ineffective when potassium was the stimulus, prevented or reduced the respiratory response, K+ loss and differential amino acid release, as well as the amino acid incorporation into protein observed with pulses and veratrine. C-6 glioma cells showed no stimulus-dependent increase in incorporation. Preliminary data, of gel electrophoretic analysis, on the proteins labelled under our conditions is presented. |
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