The deuteration of the histones of physarum polycephalum as a step towards the preparation of selectively deuterated nucleosome core particles

Abstract

AbstractPhysarum polycephalum can be grown in shake flask culture where all of the peptone component of the feed stock has been replaced by a deuterated algal hydrolysate. These conditions give approximately 35% overall deuterium incorporation into the basic nuclear proteins. This level of incorporation, together with the maintenance of a reasonable maximum growth, show P. polycephalum to be a convenient system for the preparation of nucleosome core particles with selectively deuterated histones. Selectively deuterated core particles offer considerable advantages over uniformly protonated ones when structural studies using neutron scattering are carried out.A combination of proton and deuterium magnetic resonance spectroscopy shows that under the conditions so far studied the deuterium incorporation is not uniformly distributed throughout the amino acid residues of the proteins. A 60% deuteration of the terminal apolar methyl groups is accompanied by only 28% deuteration of the hydrogen atoms bound to the α‐carbon.Our observation that α‐carbon hydrogens are exchanged in vitro reactions with 2H3O+, albeit at elevated temperature, could well indicate these hydrogens are exchanged in vivo with the solvent water of the growth medium. Suggestions are made as to other possible variations in feed stock components which could lead to a higher overall levelof deuterium incorporation.Deuteration ‐ Physarum polycephalum ‐ neutron scattering ‐ histones ‐ nucleosome core particles.