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In vitro ADP-ribosylation sites of rat liver histone H1 were determined.ADP-"Clribosyl histone H1 (average chain length = 1.1) was prepared by incubation of chromatin with 1 m~ [diose(NiWV)-"CNAD and extracted with 5% HClO.. Bisection of histone H1 with Nbromosuccinimide demonstrated that both the N H 2and COOH-terminal halves were modified.The chemical stabilities of the bonds between ADP-ribose and both of the bisected peptides were almost identical; the bonds were stable in 0.1 M HCI, but labile in 0.1 M NaOH and 2 M NHzOH (pH 7.0).Digestion of the bisected fragments with various proteases and snake venom phosphodiesterase yielded three peptides associated with '4Cribose 6-phosphate.These peptides had the amino acid sequences (N-blocked)-Ser-Glu-Thr, Ala-Pro-Ala-Glu-Lys, and Ala-Lys-Lys-Lys; the former two were obtained from the NHa-terminal half in yields of 6.0 and 2.3%, respectively, while the last was obtained from the COOH-terminal half in a yield of 6.0%.By comparison with known sequences of rabbit thymus and other histone Hl's these peptides were assigned to
Ogata et al. (Fri,) studied this question.