4N6L image
Deposition Date 2013-10-14
Release Date 2015-02-18
Last Version Date 2024-11-27
Entry Detail
PDB ID:
4N6L
Title:
Crystal structure of human cystatin E/M
Biological Source:
Source Organism:
Homo sapiens (Taxon ID: 9606)
Host Organism:
Method Details:
Experimental Method:
Resolution:
1.95 Å
R-Value Free:
0.23
R-Value Work:
0.21
R-Value Observed:
0.21
Space Group:
P 21 21 2
Macromolecular Entities
Polymer Type:polypeptide(L)
Molecule:Cystatin-M
Gene (Uniprot):CST6
Chain IDs:A
Chain Length:131
Number of Molecules:1
Biological Source:Homo sapiens
Primary Citation
Structure and mechanism of an aspartimide-dependent Peptide ligase in human legumain.
Angew.Chem.Int.Ed.Engl. 54 2917 2921 (2015)
PMID: 25630877 DOI: 10.1002/anie.201409135

Abstact

Peptide ligases expand the repertoire of genetically encoded protein architectures by synthesizing new peptide bonds, energetically driven by ATP or NTPs. Here, we report the discovery of a genuine ligase activity in human legumain (AEP) which has important roles in immunity and tumor progression that were believed to be due to its established cysteine protease activity. Defying dogma, the ligase reaction is independent of the catalytic cysteine but exploits an endogenous energy reservoir that results from the conversion of a conserved aspartate to a metastable aspartimide. Legumain's dual protease-ligase activities are pH- and thus localization controlled, dominating at acidic and neutral pH, respectively. Their relevance includes reversible on-off switching of cystatin inhibitors and enzyme (in)activation, and may affect the generation of three-dimensional MHC epitopes. The aspartate-aspartimide (succinimide) pair represents a new paradigm of coupling endergonic reactions in ATP-scarce environments.

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