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Cysteine Sulfinic Acid in the Central Nervous System: Specific Binding of [ 35 S]Cysteic Acid to Cortical Synaptic Membranes‐An Investigation of Possible Binding Sites for Cysteine Sulfinic Acid
Author(s) -
Iwata Heitaroh,
Yamagami Satoru,
Baba Akemichi
Publication year - 1982
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1982.tb07901.x
Subject(s) - cysteic acid , chemistry , cysteine , biochemistry , sulfinic acid , binding site , ligand (biochemistry) , biophysics , biology , receptor , cystine , organic chemistry , enzyme
Abstract: Specific binding sites for cysteine sulfinic acid, an excitatory amino acid, in crude synaptic membrane fractions of rat cerebral cortex were examined, using L‐[ 35 S]cysteic acid as a ligand. Two specific binding systems of [ 35 S] cystec acid were found, one Na + ‐dependent and the other Na + ‐independent. The Na + ‐independent specific binding of [ 35 S]Cysteic acid was saturable, with a K d of 474 n M and B max of 3.29 pmol/mg protein. The binding was optimal at pH 7.4 and at 37°C. Treatment of the membranes with proteases, concanavalin A, or Triton X‐100 markedly reduced the binding. Of various compounds related to cysteic acid, L‐cysteine sulfinic acid was the most effective competitor of this binding. These results indicate the existence of an Na + ‐independent specific binding site for cysteic acid in the synaptic membrane of rat cerebral cortex, which may be different from that for glutamate. Possible involvement of cysteine sulfinic acid as an endogenous ligand for this binding site is discussed.