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Insect Biochem Mol Biol

Title:		Odorant-binding protein from the stable fly (Stomoxys calcitrans) has a high-histidine N-terminal extension that binds transition metals
Author(s):		Shah JS; Buckmeier BG; Griffith W; Olafson PU; Perez de Leon AA; Renthal R;
Address:		"Department of Biology, University of Texas at San Antonio, San Antonio, TX, 78249, USA. USDA-ARS, Knipling-Bushland U.S. Livestock Insects Research Lab, Kerrville, TX, 78028, USA. Department of Chemistry, University of Texas at San Antonio, San Antonio, TX, 78249, USA. USDA-ARS, San Joaquin Valley Agricultural Sciences Center, Parlier, CA, 93648, USA. Department of Biology, University of Texas at San Antonio, San Antonio, TX, 78249, USA; Department of Neuroscience, Developmental and Regenerative Biology, University of Texas at San Antonio, San Antonio, TX, 78249, USA. Electronic address: robert.renthal@utsa.edu"
Journal Title:		Insect Biochem Mol Biol
Year:		2022
Volume:		20211231
Issue:
Page Number:		103707 -
DOI:		10.1016/j.ibmb.2021.103707
ISSN/ISBN:		1879-0240 (Electronic) 0965-1748 (Linking)
Abstract:		"The 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"
Keywords:		"Animals Binding Sites Histidine/chemistry/metabolism Insect Proteins/chemistry/*genetics/metabolism Muscidae/*genetics/metabolism Receptors, Odorant/chemistry/*genetics/metabolism Fluorescence Histidine-rich sequence Mass spectrometry Odorant-binding prot;neuroscience;"
Notes:		"MedlineShah, Jaee Shailesh Buckmeier, Beverly Greta Griffith, Wendell Olafson, Pia Untalan Perez de Leon, Adalberto A Renthal, Robert eng Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, Non-P.H.S. England 2022/01/04 Insect Biochem Mol Biol. 2022 Feb; 141:103707. doi: 10.1016/j.ibmb.2021.103707. Epub 2021 Dec 31"