title: Tetrahymena ubiquitin-histone conjugate uH2A. Isolation and structural analysis.
abstract: The ubiquitin-histone H2A conjugate, uH2A, of the protozoan Tetrahymena pyriformis was isolated by gel chromatography and octadecylsilyl-silica chromatography, from the fractions on the chromatographic purification of histone H2A [Fusauchi, Y. & Iwai, K. (1983) J. Biochem. 93, 1487-1497]. The uH2A showed an amino acid composition corresponding to the sum of an equimolar mixture of two protozoan H2A variants and protozoan free ubiquitin. N- and C-terminal sequencing of the uH2A, by Edman degradation and carboxypeptidase P digestion, showed a branched structure having two N-terminals, those of the H2A and ubiquitin components, and one C-terminal, that of each H2A variant component. Further structural analyses of the uH2A, by tryptic digestion of citraconylated uH2A and of a ubiquitinated BrCN fragment, showed that the ubiquitin C-terminal Gly-Gly is linked to the epsilon-amino group of either Lys-123, 125, or 126 in the H2A sequence, and that the ubiquitin sequence is similar to that of calf thymus but differs at least in the sequence of residues 12-27. The deducted structure was compared with the only known uH2A structure, that of calf thymus, with special reference to the branched site.
authors.forename: Y
authors.initials: Y
authors.lastname: Fusauchi
authors.forename: K
authors.initials: K
authors.lastname: Iwai
mesh_terms: D000596:Amino Acids / Q000032:analysis; D000818:Animals; D006609:High Mobility Group Proteins / Q000302:isolation & purification*; D006657:Histones / Q000302:isolation & purification*; D046911:Macromolecular Substances; D008970:Molecular Weight; D010446:Peptide Fragments / Q000032:analysis; D013768:Tetrahymena / Q000032:analysis*; D014452:Ubiquitins / Q000302:isolation & purification*
chemical_list: D000596:Amino Acids; D006609:High Mobility Group Proteins; D006657:Histones; D046911:Macromolecular Substances; D010446:Peptide Fragments; D014452:Ubiquitins