Site-specific and regiospecific installation of methylarginine analogues into recombinant histones and insights into effector protein binding.

Arginine methylation has emerged as a widespread post-translational modification with influence over myriad cellular processes. However, the molecular mechanisms underlying such methylarginine-dependent phenomena remain unclear. To aid in this research, a facile method was developed to install methylarginine analogues on recombinant protein for use in biochemical, biophysical, and structural studies. Through chemical conjugation of novel α,β-unsaturated amidine precursors with proteins, methylarginine mimics can be displayed with control of methylation site, extent, and regiospecificity. Analogue installation into histones using this strategy produced modified proteins that were recognized by antibodies specific to endogenous methylarginine, and these histones retained the capacity to form mononucleosomes. Moreover, a native methylarginine-specific binding domain was shown to interact with methylarginine analogue-modified substrates. This chemical conjugation method for installing methylarginine analogues provides an efficient route to produce homogeneous modified proteins for subsequent investigations of methylarginine-dependent processes.