Enzymatic demethylation of calf thymus histones

Enzymatic demethylation of ε-N-methyllysine residues of calf thymus histone has been investigated. Kidney contains the highest enzyme activity among the rat organs tested, and the enzyme activity is associated with the nuclear and mitocondrial fractions. Formaldehyde-C-14 is the product of demethylation of enzymatically prepared histone-methyl-C-14. Evidence indicates that demethylation occurs on the intact histone molecule.     

N-terminal acetyl-peptides from two calf thymus histones

1. The same N-terminal peptide was isolated from two major calf thymus histone fractions, F2al and F2a2. 2. The structure of the peptides is N-acetylseryl-glycyl-arginine, and the yields account for most of the N-acetyl groups previously found in these histones. 3. Some other peptides not giving a ninhydrin reaction were also investigated.     

Automatic comparison of the sequences of calf thymus histones

The sequences of five histones have been compared pairwise by means of an automatic computer-assisted procedure. All pairs are significantly similar beyond chance, pointing to a common origin for all histones. All features of the comparisons are consistent with spectroscopic data on histones' structure and interactions.     

Carbon magnetic resonance studies of the self-aggregation of calf thymus histones.

Self-aggregation of calf thymus histones H2A and H4 was studied by means of 13C magnetic resonance. Analyses of the changes in the intensities of several side-chain resonances, induced by added NaCl, confirm that carbon magnetic resonance can be used to monitor aggregation phenomena more accurately than other physicochemical methods. In particular the validity of an original computer-based method to treat 13C intensities is confirmed. The details of these aggregation phenomena are critically discussed in the light of a simple experiment on a 13C-enriched sample of H2B.