NatA engages in multi-factor complexes at the ribosomal polypeptide tunnel exit

Area of Science:

• Biochemistry
• Molecular Biology
• Proteostasis

Background:

• N-terminal acetylation (NTA) is the most prevalent co-translational protein modification in eukaryotes, essential for proteostasis.
• The NatA complex acetylates nearly 40% of the human proteome, often requiring prior N-terminal methionine excision (NME).
• Recent studies revealed NatA forming complexes with MAP1/NAC or MAP2, integrating NME and NTA functions.

Purpose of the Study:

• To investigate novel assembly mechanisms of the NatA complex.
• To explore the interaction of NatA with ribosome-associated factors (RAFs).
• To understand how NatA coordinates co-translational protein maturation.

Main Methods:

• Biochemical assays to characterize NatA complex formation.
• Analysis of interactions between NatA, RAFs, and the ribosome.
• Identification of conserved binding sites on NatA.

Main Results:

• NatA forms ribosome-independent assemblies with several RAFs.
• NatA can form ternary complexes with Ebp1 or a second NatA copy at the ribosome.
• A conserved binding site on NatA accommodates multiple RAFs (Ebp1, NAC, Naa10, HypK), forming diverse multi-factor complexes.
• These complexes are located at the ribosomal tunnel exit.

Conclusions:

• NatA acts as a central interaction hub at the ribosome.
• NatA coordinates co-translational protein maturation through interactions with RAFs.
• These findings reveal a new layer of regulation for N-terminal acetylation.