6a0i
From Proteopedia
Crystal structure of human protein N-terminal asparagine amidohydrolase (NTAN1) C75S mutant
Structural highlights
FunctionNTAN1_HUMAN N-terminal asparagine deamidase that mediates deamidation of N-terminal asparagine residues to aspartate. Required for the ubiquitin-dependent turnover of intracellular proteins that initiate with Met-Asn. These proteins are acetylated on the retained initiator methionine and can subsequently be modified by the removal of N-acetyl methionine by acylaminoacid hydrolase (AAH). Conversion of the resulting N-terminal asparagine to aspartate by NTAN1/PNAD renders the protein susceptible to arginylation, polyubiquitination and degradation as specified by the N-end rule. This enzyme does not act on substrates with internal or C-terminal asparagines and does not act on glutamine residues in any position, nor on acetylated N-terminal peptidyl Asn.[1] Publication Abstract from PubMedThe N-degron pathway is a proteolytic system in which a single N-terminal amino acid acts as a determinant of protein degradation. Especially, degradation signaling of N-terminal asparagine (Nt-Asn) in eukaryotes is initiated from its deamidation by N-terminal asparagine amidohydrolase 1 (NTAN1) into aspartate. Here, we have elucidated structural principles of deamidation by human NTAN1. NTAN1 adopts the characteristic scaffold of CNF1/YfiH-like cysteine hydrolases that features an alpha-beta-beta sandwich structure and a catalytic triad comprising Cys, His, and Ser. In vitro deamidation assays using model peptide substrates with varying lengths and sequences showed that NTAN1 prefers hydrophobic residues at the second-position. The structures of NTAN1-peptide complexes further revealed that the recognition of Nt-Asn is sufficiently organized to produce high specificity, and the side chain of the second-position residue is accommodated in a hydrophobic pocket adjacent to the active site of NTAN1. Collectively, our structural and biochemical analyses of the substrate specificity of NTAN1 contribute to understanding the structural basis of all three amidases in the eukaryotic N-degron pathway. Structural Analyses on the Deamidation of N-Terminal Asn in the Human N-Degron Pathway.,Park JS, Lee JY, Nguyen YTK, Kang NW, Oh EK, Jang DM, Kim HJ, Kim DD, Han BW Biomolecules. 2020 Jan 20;10(1). pii: biom10010163. doi: 10.3390/biom10010163. PMID:31968674[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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