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AspH is an endoplasmic reticulum (ER) membrane-anchored 2-oxoglutarate oxygenase whose C-terminal oxygenase and tetratricopeptide repeat (TPR) domains present in the ER lumen. AspH catalyses hydroxylation of asparaginyl- and aspartyl-residues in epidermal growth factor-like domains (EGFDs). Here we report crystal structures of human AspH, with and without substrate, that reveal substantial conformational changes of the oxygenase and TPR domains during substrate binding. Fe(II)-binding by AspH is unusual, employing only two Fe(II)-binding ligands (His679/His725). Most EGFD structures adopt an established fold with a conserved Cys1-3, 2-4, 5-6 disulfide bonding pattern; an unexpected Cys3-4 disulfide bonding pattern is observed in AspH-EGFD substrate complexes, the catalytic relevance of which is supported by studies involving stable cyclic peptide substrate analogues and by effects of Ca(II) ions on activity. The results have implications for EGFD disulfide pattern processing in the ER and will enable medicinal chemistry efforts targeting human 2OG oxygenases.

Original publication

DOI

10.1038/s41467-019-12711-7

Type

Journal article

Journal

Nat Commun

Publication Date

28/10/2019

Volume

10

Keywords

Amino Acid Sequence, Asparagine, Calcium-Binding Proteins, Catalytic Domain, Crystallography, Disulfides, Epidermal Growth Factor, Ferrous Compounds, Humans, Membrane Proteins, Mixed Function Oxygenases, Muscle Proteins, Protein Conformation