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J Biol Chem

Title:		Conformational change in the pheromone-binding protein from Bombyx mori induced by pH and by interaction with membranes
Author(s):		Wojtasek H; Leal WS;
Address:		"Laboratory of Chemical Prospecting, National Institute of Sericultural and Entomological Science, 1-2 Ohwashi, Tsukuba 305-8634, Japan"
Journal Title:		J Biol Chem
Year:		1999
Volume:		274
Issue:		43
Page Number:		30950 - 30956
DOI:		10.1074/jbc.274.43.30950
ISSN/ISBN:		0021-9258 (Print) 0021-9258 (Linking)
Abstract:		"The pheromone-binding protein (PBP) from Bombyx mori was expressed in Escherichia coli periplasm. It specifically bound radiolabeled bombykol, the natural pheromone for this species. It appeared as a single band both in native and SDS-polyacrylamide gel electrophoresis and was also homogeneous in most chromatographic systems. However, in ion-exchange chromatography, multiple forms sometimes appeared. Attempts to separate them revealed that they could be converted into one another. Analysis of the protein by circular dichroism and fluorescence spectroscopy demonstrated that its tertiary structure was sensitive to pH changes and that a dramatic conformational transition occurred between pH 6.0 and 5.0. This high sensitivity to pH contrasted markedly with its thermal stability and resistance to denaturation by urea. There was also no significant change in CD spectra in the presence of the pheromone. The native protein isolated from male antennae displayed the same changes in its spectroscopic properties as the recombinant material, demonstrating that this phenomenon is not an artifact arising from the expression system. This conformational transition was reproduced by interaction of the protein with anionic (but not neutral) phospholipid vesicles. Unfolding of the PBP structure triggered by membranes suggests a plausible mechanism for ligand release upon interaction of the PBP-pheromone complex with the surface of olfactory neurons. This pH-linked structural flexibility also explains the heterogeneity reported previously for B. mori PBP and other members of this class of proteins"
Keywords:		"Animals Bombyx Carrier Proteins/*chemistry/isolation & purification Chromatography, Ion Exchange Circular Dichroism Cloning, Molecular Electrophoresis, Polyacrylamide Gel Escherichia coli *Hydrogen-Ion Concentration Insect Proteins/*chemistry/isolation &;"
Notes:		"MedlineWojtasek, H Leal, W S eng Research Support, Non-U.S. Gov't 1999/10/16 J Biol Chem. 1999 Oct 22; 274(43):30950-6. doi: 10.1074/jbc.274.43.30950"