Understanding Absolute Stoichiometry of Oligomeric Protein Complexes Using SEC-MALS

Nucleosome assembly proteins (Naps) are histone chaperones that interact with histones H2A-H2B and/or H3-H4 in the regulation of chromatin architecture. Determining the stoichiometry of Nap-histone complexes has been challenging due to two major factors: Naps undergo dynamic oligomerization that is influenced by salt concentration; and H3-H4 forms a hetero-tetramer. Using SEC-MALS, researchers have determined the absolute stoichiometry of Nap-histone complexes containing Nap orthologs, a new Nap paralog, and relevant deletion constructs.