30HI

Ternary complex of translating ribosome, NAC and NatB

This is a non-PDB format compatible entry.

Summary for 30HI

• Entry DOI: 10.2210/pdb30hi/pdb
• Related: 28LN
• EMDB information: 57771
• Descriptor: Xbp1u stalled ANXA4 nascent chain, 60S ribosomal protein L5, Large ribosomal subunit protein eL6, ... (93 entities in total)
• Functional Keywords: cotranslational n-terminal acetylation, n-terminal acetyltransferase b (natb), nascent polypeptide-associated complex (nac), translating ribosome, translation
• Biological source: Homo sapiens; More
• Total number of polymer chains: 89
• Total formula weight: 4086504.10

Authors

Knejski, P.,Scaiola, A.,Leibundgut, M.,Ban, N. (deposition date: 2026-04-25, release date: 2026-10-07)

Primary citation

Silva Alves, N.,Knejski, P.,Scaiola, A.,Leibundgut, M.,Gamerdinger, M.,Ban, N.,Deuerling, E.
Structural basis of cotranslational protein N-terminal acetylation by NatB in human cells.
Nat Commun, 17:-, 2026

PubMed Abstract: Cotranslational N-terminal acetylation is a widespread modification that shapes protein stability, localization, and function in eukaryotic cells. The essential human NatB complex (NAA25-NAA20) acetylates the initiator methionine of a substantial fraction of the proteome, yet how NatB engages translating ribosomes has remained unclear. Here we define the cotranslational mechanism underlying NatB function. NatB is recruited by the nascent polypeptide-associated complex (NAC) through a high-affinity interaction between the NACα UBA domain and the auxiliary subunit NAA25, while both NatB subunits form additional contacts with the ribosomal surface near the tunnel exit. Together, these interactions position the NatB active site directly adjacent to the emerging nascent chain, enabling efficient modification of newly synthesized proteins. Structural comparisons reveal a conserved ribosome-binding architecture shared with other N-acetyltransferases, including NatA/E and NatD, implying mutually exclusive ribosome occupancy. Together with prior work, these findings establish NAC as a central organizer of cotranslational N-terminal processing.

PubMed: 42436108
DOI: 10.1038/s41467-026-75207-1

Experimental method

ELECTRON MICROSCOPY (3.2 Å)