NatB complex

GO:0031416 · Other · Multiprotein complex · Proposed

A conserved complex that catalyzes the transfer of an acetyl group to the N-terminal residue of a protein acceptor molecule that has a Met-Glu, Met-Asp, Met-Asn, or Met-Met N-terminus. In Saccharomyces the complex includes Nat3p and Mdm20p. [GO:0031416]

Synonyms: N-terminal acetyltransferase B complex

UniProt location names: UniProt Consortium, CC BY 4.0. Reference label and route sources.

Components

Component	Type	Part of / acts on	Grounding	Genes	Stoichiometry	Essential	Role
Nat3 NatB catalytic subunit	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	NAT3		UNKNOWN	Catalytic constituent of the budding-yeast NatB complex that works with Mdm20 to provide N-terminal acetyltransferase activity. `DOI:10.1074/jbc.M304690200` Polevoda et al. 2003 report that Saccharomyces cerevisiae NatB is composed of interacting Nat3p and Mdm20p subunits, both required for NatB acetyltransferase activity. `DOI:10.1016/s0006-291x(03)01316-0` Polevoda and Sherman 2003 review the eukaryotic N-terminal acetyltransferase complexes and describe yeast NatB as the Nat3p catalytic subunit with the Mdm20p auxiliary subunit.
Mdm20 NatB auxiliary subunit	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	MDM20		UNKNOWN	Auxiliary constituent of the budding-yeast NatB complex that interacts with Nat3 and is required for NatB activity. `DOI:10.1074/jbc.M304690200` Polevoda et al. 2003 report that Saccharomyces cerevisiae NatB is composed of interacting Nat3p and Mdm20p subunits, both required for NatB acetyltransferase activity. `DOI:10.1016/s0006-291x(03)01316-0` Polevoda and Sherman 2003 review the eukaryotic N-terminal acetyltransferase complexes and describe yeast NatB as the Nat3p catalytic subunit with the Mdm20p auxiliary subunit.

Taxonomic distribution

NCBITaxon:4932 Saccharomyces cerevisiae — COMMON: Polevoda et al. 2003 characterized Nat3p and Mdm20p as interacting NatB subunits in Saccharomyces cerevisiae. [DOI:10.1074/jbc.M304690200]

Canonical examples

NCBITaxon:4932 Saccharomyces cerevisiae — Budding yeast is the source organism in which Nat3p and Mdm20p were shown to form the NatB Nalpha-terminal acetyltransferase. [DOI:10.1074/jbc.M304690200]

Functions

protein-N-terminal amino-acid acetyltransferase activity GO:0004596 — Transfer of an acetyl group from acetyl-CoA to the N-terminal alpha-amino group of NatB substrate proteins.
- GO:0004596 GO:0004596 is the Gene Ontology molecular-function term for protein-N-terminal amino-acid acetyltransferase activity.
- GO:0031416 GO:0031416 defines the NatB complex by transfer of acetyl groups to N-terminal Met-Glu, Met-Asp, Met-Asn or Met-Met protein residues.
- DOI:10.1074/jbc.M304690200 Polevoda et al. 2003 describe budding-yeast NatB as an Nalpha-terminal acetyltransferase that acts on proteins with Met-Glu or Met-Asp N-termini and subclasses with Met-Asn or Met-Met N-termini.

Mechanism graphs

NatB carries yeast N-terminal acetyltransferase activity (FUNCTION)

In Saccharomyces cerevisiae, Nat3 and Mdm20 form a NatB complex that supports protein-N-terminal acetyltransferase activity.

Subject	Predicate	Object	Evidence
Nat3 NatB catalytic subunit	contributes to	NatB complex	`DOI:10.1074/jbc.M304690200` Polevoda et al. 2003 report that Saccharomyces cerevisiae NatB is composed of interacting Nat3p and Mdm20p subunits, both required for NatB acetyltransferase activity. `DOI:10.1016/s0006-291x(03)01316-0` Polevoda and Sherman 2003 review the eukaryotic N-terminal acetyltransferase complexes and describe yeast NatB as the Nat3p catalytic subunit with the Mdm20p auxiliary subunit.
Mdm20 NatB auxiliary subunit	contributes to	NatB complex	`DOI:10.1074/jbc.M304690200` Polevoda et al. 2003 report that Saccharomyces cerevisiae NatB is composed of interacting Nat3p and Mdm20p subunits, both required for NatB acetyltransferase activity. `DOI:10.1016/s0006-291x(03)01316-0` Polevoda and Sherman 2003 review the eukaryotic N-terminal acetyltransferase complexes and describe yeast NatB as the Nat3p catalytic subunit with the Mdm20p auxiliary subunit.
NatB complex	supports	protein-N-terminal amino-acid acetyltransferase activity	`GO:0004596` GO:0004596 is the Gene Ontology molecular-function term for protein-N-terminal amino-acid acetyltransferase activity. `DOI:10.1074/jbc.M304690200` Polevoda et al. 2003 characterized Nat3p and Mdm20p as interacting budding-yeast NatB subunits required for acetyltransferase activity.

Discussions

CURATION_TODO (OPEN): Resolve exact source-neutral family groundings for the curated budding-yeast NatB constituents.

Evidence

GO:0031416 Gene Ontology cellular-component term for NatB complex and its exact N-terminal acetyltransferase B complex synonym.
GO:0031414 Gene Ontology cellular-component parent term for N-terminal protein acetyltransferase complexes.
GO:0004596 Gene Ontology molecular-function term for protein-N-terminal amino-acid acetyltransferase activity.
PMID:12783868 PubMed identifier for Polevoda et al. 2003, the budding-yeast NatB composition paper.
DOI:10.1074/jbc.M304690200 DOI for Polevoda et al. 2003, 'Nat3p and Mdm20p are required for function of yeast NatB Nalpha-terminal acetyltransferase and of actin and tropomyosin', verified through NCBI E-utilities.
PMID:12890471 PubMed identifier for Polevoda and Sherman 2003, the eukaryotic N-terminal acetyltransferase subunit review cited by GO:0031416.
DOI:10.1016/s0006-291x(03)01316-0 DOI for Polevoda and Sherman 2003, 'Composition and function of the eukaryotic N-terminal acetyltransferase subunits', verified through NCBI E-utilities.

Curation history

2026-09-26T09:23:11Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-26T09:24:07Z codex · EXPANDED_RECORD — Added NatB exact synonymy, N-terminal protein acetyltransferase parentage, two budding-yeast constituent rows, yeast scope, protein-N-terminal acetyltransferase function, GO/PubMed/DOI evidence, a nonmechanistic function graph, and a subunit-grounding TODO.
2026-09-26T09:25:10Z codex · NORMALIZED_RECORD — Re-emitted repeated NatB evidence entries without YAML aliases.

Source: data/structures/other/natb_complex.yaml