title: Reactivity of individual functional groups of histones in calf thymus chromatin.
abstract: Using the technique of competitive labelling (Kaplan, H., Stevenson, K.J. and Hartley, B.S. (1971) Biochem. J. 124, 289-299) with 1-fluoro-2,4-dinitro-[3,5-3H]benzene ([3H]Dnp-F), the chemical reactivity of the alanyl amino-terminus of H3, the prolyl amino-terminus of H2B and the sulphydryl groups of H3 within calf thymus chromatin were determined. Over pH values from 6 to 10, none of the groups had pH-reactivity profiles which fit titration curves, indicating that they are involved in specific interactions with other structural elements of chromatin. The alanyl amino-terminus is completely nonreactive over the entire pH range studied. The prolyl amino-terminus is reactive but its reactivity is considerably lower than expected for a secondary amino group. An unusual feature of this group is that its pH-reactivity profile has sharp discontinuities at pH values of 7.8 and 9. The average reactivity of the two sulphydryl groups of H3, unlike the two amino-termini, appears to approximate that expected of a free sulphydryl group.
mesh_terms: D000409:Alanine / Q000378:metabolism; D000818:Animals; D002417:Cattle; D002843:Chromatin / Q000378:metabolism*; D004139:Dinitrofluorobenzene / Q000494:pharmacology; D006657:Histones / Q000302:isolation & purification / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D011392:Proline / Q000378:metabolism; D013438:Sulfhydryl Compounds / Q000378:metabolism; D013950:Thymus Gland / Q000378:metabolism*
chemical_list: D002843:Chromatin; D006657:Histones; D013438:Sulfhydryl Compounds; D011392:Proline; D004139:Dinitrofluorobenzene; D000409:Alanine