| Title: | Kinetics and molecular properties of pheromone binding and release |
| Author(s): | Leal WS; Chen AM; Ishida Y; Chiang VP; Erickson ML; Morgan TI; Tsuruda JM; |
| Address: | "Maeda-Duffey Laboratory, Department of Entomology, University of California, Davis, CA 95616, USA. wsleal@ucdavis.edu" |
| ISSN/ISBN: | 0027-8424 (Print) 1091-6490 (Electronic) 0027-8424 (Linking) |
| Abstract: | "Transient kinetic studies have shown that the uptake of the pheromone (bombykol) of the silkworm moth (Bombyx mori), by its pheromone-binding protein (PBP) BmorPBP, proceeds with an 'on' rate of 0.068 +/- 0.01 microM(-1).s(-1). With the high concentration of PBP in the sensillar lymph (10 mM), the half-life for the uptake of pheromone in vivo is approximately equal to 1 ms. A pH-dependent conformational change (BmorPBP(B) --> BmorPBP(A)), associated with the release of pheromone, is a first-order reaction (k = 74.1 +/- 0.32 s(-1); t(1/2), 9.3 ms). Under physiological conditions, both reactions proceed with half-life times on the order of milliseconds, as is required for odorant-oriented navigation in insects. Molecular interactions of bombykol with both native and mutated PBPs were analyzed by a novel binding assay. A recombinant protein with the native conformation (BmorPBP) showed high binding affinity (K(D) = 105 nM) at pH 7 but low affinity (K(D) = 1,600 nM) at pH 5, when tested at both low and high KCl concentrations. A protein with a C-terminal segment deleted (BmorPBPDeltaP129-V142) was found to bind bombykol at pH 7 and at pH 5 with the same affinity as the native protein at pH 7, indicating that the C-terminal segment is essential for preventing binding at low pH. Binding studies with three mutated proteins (BmorPBPW37F, BmorPBPW127F, and BmorPBPW37A) showed that replacing Trp-37 (with Phe or Ala) or Trp-127 (with Phe) did not affect the binding affinity to bombykol. Fluorescence studies shed light on the contributions of Trp-37 and Trp-127 emissions to the overall fluorescence" |
| Keywords: | "Animals Bombyx Carrier Proteins/chemistry/*metabolism Fatty Alcohols/*chemistry/*metabolism Half-Life Hydrogen-Ion Concentration Insect Proteins/chemistry/*metabolism Intercellular Signaling Peptides and Proteins Kinetics Models, Molecular Pheromones/*che;" |
| Notes: | "MedlineLeal, Walter S Chen, Angela M Ishida, Yuko Chiang, Vicky P Erickson, Melissa L Morgan, Tania I Tsuruda, Jennifer M eng U01 AI058267/AI/NIAID NIH HHS/ 1U01 AI 058267-01/AI/NIAID NIH HHS/ Research Support, N.I.H., Extramural Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, Non-P.H.S. Research Support, U.S. Gov't, P.H.S. 2005/03/24 Proc Natl Acad Sci U S A. 2005 Apr 12; 102(15):5386-91. doi: 10.1073/pnas.0501447102. Epub 2005 Mar 22" |
