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Mechanisms of Olfaction in Insects - ResearchSpace@Auckland ...

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3.1 Introduction<br />

3<br />

The roles <strong>of</strong> Epiphyas<br />

postvittana GOBP2 <strong>in</strong><br />

odour detection by<br />

EpOR1<br />

The abundance <strong>of</strong> odorant b<strong>in</strong>d<strong>in</strong>g prote<strong>in</strong>s <strong>in</strong> the sensillum lymph poses numerous<br />

questions about their function. Although OBPs were discovered <strong>in</strong> <strong>in</strong>sects nearly two<br />

decades before the odorant receptors, there cont<strong>in</strong>ues to be much debate over their<br />

roles(s). Several roles for OBPs have been postulated based on experimental data<br />

obta<strong>in</strong>ed from studies <strong>of</strong> PBPs. These prote<strong>in</strong>s form a family with 32–92% sequence<br />

identity <strong>in</strong> moths (Abraham et al., 2005). They are present at high concentrations <strong>in</strong><br />

the range <strong>of</strong> 10 µM <strong>in</strong> the sensillum lymph (Kle<strong>in</strong>, 1987) and have a role <strong>in</strong><br />

pheromone b<strong>in</strong>d<strong>in</strong>g (Vogt and Riddiford, 1981; Vogt et al., 1989; Maibeche-Coisne et<br />

al., 1997; Newcomb et al., 2002). OBPs are thought to form complexes with ligands<br />

and have been suggested to: aid the solubilisation and transport <strong>of</strong> ligands; protect<br />

ligands from enzymatic degradation <strong>in</strong> the sensillum lymph; enable <strong>in</strong>teraction <strong>of</strong><br />

ligands with dendritic bound ORs, and facilitate deactivation <strong>of</strong> the ligand (see section<br />

1.5.1 for a detailed overview on the roles <strong>of</strong> OBPs).

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