Human histidine triad nucleotide binding protein 1 (hHint1) is a purine nucleoside phosphoramidase and adenylate hydrolase that has emerged as a potential therapeutic target for the management of pain. However, the molecular mechanism of Hint1 in the signaling pathway has remained less clear. The role of metal ions in regulating postsynaptic transmission is well known, and the active site of hHint1 contains multiple histidines. Here we have investigated the effect of divalent metal ions (Cd2+, Cu2+, Mg2+, Mn2+, Ni2+, and Zn2+) on the structural integrity and catalytic activity of hHint1. With the exception of Mg2+, all the divalent ions inhibited hHint1, the rank of order was found to be Cu2+ >Zn2+ >Cd2+ ≥Ni2+ >Mn2+ based on their IC50 and kin/KI values. A crystal structure of hHint1 with bound Cu2+ is described to explain the competitive reversible inactivation of hHint1 by divalent cations. All the metal ions exhibited time- and concentration- dependent inhibition, with the rate of inactivation highly dependent on alterations of the C-terminus. With the exception of Cu2+; restoration of inhibition was observed for all the metal ions after treatment with EDTA. Our studies reveal a loss in secondary structure and aggregation of hHint1 upon incubation with 10-fold excess of copper. Thus, hHint1 appears to be structurally sensitive to irreversible inactivation by copper, which may be of neurotoxicological and pharmacological significance.
|Original language||English (US)|
|Number of pages||7|
|Journal||Biochemical and Biophysical Research Communications|
|State||Published - Sep 23 2017|
Bibliographical noteFunding Information:
The authors are grateful to Jay Nix of the Molecular Biology Consortium of ALS Beamline 4.2.2 for crystallographic data collection and processing. KMM was supported by the University of Minnesota Frieda Martha Kunze Fellowship and the American Foundation for Pharmaceutical Education. Funding from the University of Maryland Extension is gratefully acknowledged. Funding from the University of Minnesota Foundation is gratefully acknowledged.
© 2017 Elsevier Inc.
Copyright 2017 Elsevier B.V., All rights reserved.
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