5sy4
Atomic resolution structure of reduced E. coli YajL
Structural highlights
FunctionYAJL_ECOLI Protein deglycase that repairs methylglyoxal- and glyoxal-glycated amino acids and proteins, and releases repaired proteins and lactate or glycolate, respectively. Deglycates cysteines, arginines and lysines residues in proteins, and thus reactivates these proteins by reversing glycation by glyoxals. Acts on early glycation intermediates (hemithioacetals and aminocarbinols), preventing the formation of advanced glycation endproducts (AGE) (PubMed:25416785) (By similarity). Displays a covalent chaperone activity with sulfenylated thiol proteins by forming mixed disulfides with members of the thiol proteome, and preferentially with sulfenylated cellular proteins, upon oxidative stress; these mixed disulfides can be subsequently reduced by low-molecular-weight thiols to regenerate YajL and reduced proteins (PubMed:22157000, PubMed:22321799). Involved in biogenesis of ribosomal proteins, probably as a ribosomal protein-folding chaperone. Confers resistance to oxidative stress. The chaperone activity reported for YajL is probably recruited to execute its deglycase activity, to interact with non-native glycated proteins and gain access to partially buried glycated sites.[UniProtKB:Q99497][1] [2] [3] [4] [5] Publication Abstract from PubMedShort hydrogen bonds (H-bonds) have been proposed to play key functional roles in several proteins. The location of the proton in short H-bonds is of central importance, as proton delocalization is a defining feature of low-barrier hydrogen bonds (LBHBs). Experimentally determining proton location in H-bonds is challenging. Here, bond length analysis of atomic (1.15-0.98 A) resolution X-ray crystal structures of the human protein DJ-1 and its bacterial homologue, YajL, was used to determine the protonation states of H-bonded carboxylic acids. DJ-1 contains a buried, dimer-spanning 2.49 A H-bond between Glu15 and Asp24 that satisfies standard donor-acceptor distance criteria for a LBHB. Bond length analysis indicates that the proton is localized on Asp24, excluding a LBHB at this location. However, similar analysis of the Escherichia coli homologue YajL shows both residues may be protonated at the H-bonded oxygen atoms, potentially consistent with a LBHB. A Protein Data Bank-wide screen identifies candidate carboxylic acid H-bonds in approximately 14% of proteins, which are typically short [dO-O = 2.542(2) A]. Chemically similar H-bonds between hydroxylated residues (Ser/Thr/Tyr) and carboxylates show a trend of lengthening O-O distance with increasing H-bond donor pKa. This trend suggests that conventional electronic effects provide an adequate explanation for short, charge-assisted carboxylic acid-carboxylate H-bonds in proteins, without the need to invoke LBHBs in general. This study demonstrates that bond length analysis of atomic resolution X-ray crystal structures provides a useful experimental test of certain candidate LBHBs. Short Carboxylic Acid-Carboxylate Hydrogen Bonds Can Have Fully Localized Protons.,Lin J, Pozharski E, Wilson MA Biochemistry. 2016 Dec 30. doi: 10.1021/acs.biochem.6b00906. PMID:27989121[6] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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