6hd7
From Proteopedia
Cryo-EM structure of the ribosome-NatA complex
Structural highlights
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Function[RL11A_YEAST] Binds to 5S ribosomal RNA. [RL40A_YEAST] Ubiquitin: Exists either covalently attached to another protein, or free (unanchored). When covalently bound, it is conjugated to target proteins via an isopeptide bond either as a monomer (monoubiquitin), a polymer linked via different Lys residues of the ubiquitin (polyubiquitin chains) or a linear polymer linked via the initiator Met of the ubiquitin (linear polyubiquitin chains). Polyubiquitin chains, when attached to a target protein, have different functions depending on the Lys residue of the ubiquitin that is linked: Lys-6-linked may be involved in DNA repair; Lys-11-linked is involved in ERAD (endoplasmic reticulum-associated degradation) and in cell-cycle regulation; Lys-29-linked is involved in lysosomal degradation; Lys-33-linked is involved in kinase modification; Lys-48-linked is involved in protein degradation via the proteasome; Lys-63-linked is involved in endocytosis, and DNA-damage responses. Linear polymer chains formed via attachment by the initiator Met lead to cell signaling. Ubiquitin is usually conjugated to Lys residues of target proteins, however, in rare cases, conjugation to Cys or Ser residues has been observed. When polyubiquitin is free (unanchored-polyubiquitin), it also has distinct roles, such as in activation of protein kinases, and in signaling (By similarity). 60S ribosomal protein L40-A: Component of the ribosome, a large ribonucleoprotein complex responsible for the synthesis of proteins in the cell. The small ribosomal subunit (SSU) binds messenger RNAs (mRNAs) and translates the encoded message by selecting cognate aminoacyl-transfer RNA (tRNA) molecules. The large subunit (LSU) contains the ribosomal catalytic site termed the peptidyl transferase center (PTC), which catalyzes the formation of peptide bonds, thereby polymerizing the amino acids delivered by tRNAs into a polypeptide chain. The nascent polypeptides leave the ribosome through a tunnel in the LSU and interact with protein factors that function in enzymatic processing, targeting, and the membrane insertion of nascent chains at the exit of the ribosomal tunnel (PubMed:22096102). eL40 is essential for translation of a subset of cellular transcripts, including stress response transcripts, such as DDR2 (PubMed:23169626).[1] [2] [ARD1_YEAST] Catalytic component of the NatA N-terminal acetyltransferase, which catalyzes acetylation of proteins beginning with Met-Ser, Met-Gly and Met-Ala. N-acetylation plays a role in normal eukaryotic translation and processing, protect against proteolytic degradation and protein turnover.[3] [RL4A_YEAST] Participates in the regulation of the accumulation of its own mRNA.[4] [RL5_YEAST] Binds 5S RNA and is required for 60S subunit assembly. [NAT1_YEAST] Non-catalytic component of the NatA N-terminal acetyltransferase, which catalyzes acetylation of proteins beginning with Met-Ser, Met-Gly and Met-Ala. N-acetylation plays a role in normal eukaryotic translation and processing, protect against proteolytic degradation and protein turnover. NAT1 anchors ARD1 and NAT5 to the ribosome and may present the N termini of nascent polypeptides for acetylation.[5] [6] [RL25_YEAST] This protein binds to a specific region on the 26S rRNA. [NAT5_YEAST] Non-essential component of the NatA N-terminal acetyltransferase, which catalyzes acetylation of proteins beginning with Met-Ser, Met-Gly and Met-Ala. N-acetylation plays a role in normal eukaryotic translation and processing, protect against proteolytic degradation and protein turnover. [RL37A_YEAST] Binds to the 23S rRNA (By similarity). Publication Abstract from PubMedThe majority of eukaryotic proteins are N-terminally alpha-acetylated by N-terminal acetyltransferases (NATs). Acetylation usually occurs co-translationally and defects have severe consequences. Nevertheless, it is unclear how these enzymes act in concert with the translating ribosome. Here, we report the structure of a native ribosome-NatA complex from Saccharomyces cerevisiae. NatA (comprising Naa10, Naa15 and Naa50) displays a unique mode of ribosome interaction by contacting eukaryotic-specific ribosomal RNA expansion segments in three out of four binding patches. Thereby, NatA is dynamically positioned directly underneath the ribosomal exit tunnel to facilitate modification of the emerging nascent peptide chain. Methionine amino peptidases, but not chaperones or signal recognition particle, would be able to bind concomitantly. This work assigns a function to the hitherto enigmatic ribosomal RNA expansion segments and provides mechanistic insights into co-translational protein maturation by N-terminal acetylation. Ribosome-NatA architecture reveals that rRNA expansion segments coordinate N-terminal acetylation.,Knorr AG, Schmidt C, Tesina P, Berninghausen O, Becker T, Beatrix B, Beckmann R Nat Struct Mol Biol. 2018 Dec 17. pii: 10.1038/s41594-018-0165-y. doi:, 10.1038/s41594-018-0165-y. PMID:30559462[7] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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