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Answer:
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1. Three enzymes which transferred acetate from acetyl coenzyme A specifically to histones were extracted from rat thymus nuclei or chromatin by sonication in the presence of 1 M (NH4)2 SO4.
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2. Two fractions having histone acetyltransferase activity (A and B) were separated by DEAE-cellulose chromatography. Enzyme Fraction B was separated into two enzymes (B1 and B2) by gel filtration on Sephadex G-200. All three acetyltransferases were further purified by chromatography on hydroxylapatite.
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3. The approximate molecular weights according to Sephadex G-200 chromatography and sucrose gradient centrifugation were 99 000, 110 000 and 92 000 for the enzymes A, B1 and B2, respectively.
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4. The pI of the enzyme A as estimated by isoelectric focusing was 5.9, the enzymes B1 and B2 were isoelectric at pH 4.75.
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5. p-Chloromercuribenzoate inhibited the activity of the B enzymes and the formation of an acyl-enzyme complex.
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6. Acetyltransferase A preferentially acetylated histone Fraction fr and in addition poly-l-lysine, resulting in the formation of ε-N-acetyllysine. The enzymes B1 and B2 preferred histone f2a1 as their substrate, histone f3 and poly-l-lysine were not acetylated. Two as yet unidentified acetylated amino acid derivatives were obtained from a digest of histone f2a1 acetylated by the B enzymes.