Co-translational interface formation in N-terminal acetyltransferase complexes

N-terminal (Nt)-acetylation is a highly prevalent protein modification in both prokaryotes and eukaryotes. It is an ancient and ubiquitous co-translational modification catalyzed by a highly conserved family of N-terminal acetyltransferases (NATs). Prokaryotes have at least 3 NATs and Nt- acetylation is conducted by individually acting Nt-acetyltransferases Humans have six highly conserved NATs, suggesting an increase in regulatory complexity of this modification during eukaryotic evolution. In eukaryotes this modification is catalyzed by complexes, often composed of a catalytic subunit and an auxiliary subunit, which provides ribosome association. Thus, enabling co-translational (Nt)-acetylation of most nascent chains, to influence multiple processes such as cell cycle progression, heat-shock resistance, mating, telomeric silencing and mitophagy.

Our study suggests evolutionary advantage of Nats functional complex over individual units, facilitating the achievement of localization and folding. Using molecular dynamics, we identified residues at the interface critical for complex stability (hotspots) for NatA and NatB complexes, in Saccharomyces cerevisiae. We utilized the CRISPR/Cas9 method to study the impact of point mutations on co-translational assembly interactions as well as co-translational Nats function.

Our work demonstrated the in vivo requirements for co-translational interface formation and its impact on the functionality and stability of different complex subunits.