首页|Odorant-binding protein from the stable fly (Stomoxys calcitrans) has a high-histidine N-terminal extension that binds transition metals
Odorant-binding protein from the stable fly (Stomoxys calcitrans) has a high-histidine N-terminal extension that binds transition metals
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NSTL
Elsevier
? 2021The role of odorant- and pheromone-binding proteins (OBPs) in olfactory function is not fully understood. We found an OBP sequence from the stable fly, Stomoxys calcitrans, ScalOBP60, that has a 25 amino acid N-terminal extension with a high content of histidine and acidic amino acids, suggesting a possible metal binding activity. A search of public databases revealed a large number of other fly OBPs with histidine-rich N-terminal extensions, as well as beetle, wasp and ant OBPs with histidine-rich C-terminal extensions. We recombinantly expressed ScalOBP60, as well as a truncated sequence which lacks the histidine-rich N-terminal region, tScalOBP60. Using fluorescence quenching and electrospray quadrupole time-of-flight mass spectrometry (ESI-QTOF), we detected two different types of metal-binding sites. Divalent copper, nickel and zinc bind to the N-terminal histidine-rich region, and divalent copper binds to an internal sequence position. Comparison of the ESI-QTOF spectra of ScalOBP60 and tScalOBP60 showed that the histidine-rich sequence is structurally disordered, but it becomes more ordered in the presence of divalent metal. When copper is bound to the internal site, binding of a hydrophobic ligand to ScalOBP60 is inhibited. The internal and N-terminal metal sites interact allosterically, possibly through a conformational equilibrium, suggesting a mechanism for metal regulation of ligand binding to ScalOBP60. Based on our studies of ScalOBP60, we propose several possible olfactory and non-olfactory functions for this OBP.
FluorescenceHistidine-rich sequenceMass spectrometryOdorant-binding proteinOlfactionTransition metal binding
Perez de Leon A.A.、Renthal R.、Buckmeier B.G.、Olafson P.U.、Griffith W.、Shah J.S.
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USDA-ARS San Joaquin Valley Agricultural Sciences Center
Department of Biology University of Texas at San Antonio
USDA-ARS Knipling-Bushland U.S. Livestock Insects Research Lab
Department of Chemistry University of Texas at San Antonio
NSTL
Elsevier
