Evidence for two conformational forms of monhistone protein BA which differ in their affinity for DNA |
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Authors: | Frank C Bennett Barry I Rosenfeld Cheng-Hsiung Huang Lynn C Yeoman |
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Institution: | Nuclear Protein Laboratory Department of Pharmacology Baylor College of Medicine Houston, Texas 77030 USA |
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Abstract: | Nonhistone protein BAfree was purified from the 0.075 M NaCl/0.025 M 8 extract of whole rat liver nuclei while protein BAbound was isolated from the 0.05 M Na2HPO4/8 M urea/1% β-mercaptoethanol/pH 7.6 extract of dehistonized rat liver chromatin. Chromatin associated protein BAbound was able to bind 60% of the 3H] DNA in a nitrocellulose filter binding assay while nucleoplasmic protein BAfree showed essentially no DNA binding activity. Circular dichroism analysis of the two forms of protein BA revealed substantial differences in their conformations. Protein BAfree was found to have an α-helix content of 41% while protein BAbound displayed a spectrum more typical of unordered or β-turn structures. |
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