Fig. 2: NAT machinery, conservation and Nt-acetylome in eukaryotes.

A The eukaryotic family of N-terminal acetyltransferases (NATs) comprises eight enzyme types (NatA–NatH). NatA–NatE act co-translationally, modifying nascent polypeptides during their synthesis on the ribosome. In contrast, NatF–NatH operate post-translationally, targeting proteins after their synthesis⁶. NatF is localised on the cytosolic side of the Golgi apparatus (and of the plasma membrane in plants), modifying transmembrane proteins^9,10. NatG is associated with plastids^7,8, and NatH specifically Nt-acetylates actins¹¹. The catalytic subunits of each NAT are designated NAA10–NAA90, with some NATs requiring auxiliary subunits (NAA15, HYPK, NAA25, NAA35, NAA38 and PFN2) for ribosome anchoring and modulation of enzymatic activity. Each NAT complex exhibits distinct substrate specificity, primarily determined by the first two to four amino acids. The indicated substrate specificity is defined by human and/or yeast NATs (and appears to be similar in plants), except for NatG, which is based on plant enzymes^6,8. B All co-translational NATs (NatA–NatE) are conserved from yeast to metazoans and plants, but yeast NatE is likely catalytically inactive. NatF is present in both plants and metazoans, whereas NatG is exclusive to plants and NatH is only found in metazoans⁶. C Approximately 50–80% of the eukaryotic proteome is N-terminally acetylated (Nt-acetylome). In yeast, metazoans and plants, NatA accounts for the largest share of the Nt-acetylome, followed by NatB. NatC, NatE and NatF have overlapping substrate specificities in vitro, with varying coverage of the Nt-acetylome in eukaryotes^4,5,6.