MICROHETEROGENEITY OF BRAIN CYTOPLASMIC AND SYNAPTOPLASMIC ACTINS |
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| Authors: | Charles A Marotta Paola Strocchi Jeffrey M Gilbert |
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| Institution: | Neurochemistry Laboratory, Mailman Research Center, McLean Hospital, Belmont, MA 02178, U.S.A.;The Department of Psychiatry, Massachusetts General Hospital and Harvard Medical School, Boston, MA, U.S.A. |
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| Abstract: | Abstract— Actin present in whole rat brain cytoplasm and in synaptosomes was purified by DNase I affinity chromatography. By use of two-dimensional gels and one-dimensional isoelectric focusing gels, brain actin was shown to be composed of two isomeric forms. By comparison with muscle actins, brain actins were identified as the β and γ isomers. Muscle type α actin is not present in brain. Synaptosomal protein with high affinity for DNase I is primarily composed of β and γ actin, however, two minor synaptosomal proteins, S1 and S2, with similar DNase I affinity were also isolated. S11 and S2 have the same apparent molecular weight as whole brain actin, are more acidic than the major actin forms and are distinct from a actin. Relative to β and γ actin, the content of S1 and S2 is 3-fOld greater in synaptosomes when compared to similar non-synaptosomal species. The results demonstrate heterogeneity of brain actins and compartmentalization of brain proteins with high affinity for DNase I at the synapse. It was also shown that tubulin has selective affinity for the DNase I-actin complex. |
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