Summary1The cotton bollworm H. armigera, which feeds on important crops e.g. Cotton, Tomatoes,Corn, Soyebeans etc, is causing detrimental damage every year worldwide, negativelyaffecting the agricultural economic production. The need is to look for morepronounced and effective insecticides. Cholesterol is the intermediate precursorof steroid hormones in insects and plays a pivotal role in their embryology andreproduction.
Sterol carrier gene (SCP-2) possesses cholesterol binding sitesand is responsible for cholesterol uptake, transfer and accumulation during insect’sontogeny. The present study was conducted to evaluate the structure andfunction of SCP-2 protein as a potential target to develop novel insecticidesagainst H. armigera.
In order to address the research questions, recombinantprotein was made by theconstruction of HaSCP-2 recombinant plasmid. Protein was purified and itsstructure and function was elucidated by NMR spectroscopy. Then Interactionof HaSCP-2 with lipid and sterol molecules was carried out by the dockingsimulation which indicated that lipid such as cholesterol, ?–sitosterol and palmitic acid could bind to HaSCP-2 withhigh docking scores, suggested that HaSCP-2 may interact with cholesterol orfatty acids through these important sites. Furthermore, NBD-cholesterol binding assays wereperformed to investigate ligand binding activity of HaSCP-2.
It demonstratedthat HaSCP-2 may play an important role in the cholesterol absorption andtransportation in the cotton bollworm.It was further confirmed by mutagenesis experiments which indicated Y51,F53, F89, F110, I117 and Q131 may be the key functional sites involvedin the intracellular hydrophobic interaction between HaSCP-2 and cholesterolwhich serves as a sieve for the transportation of sterol. High cholesterolbinding activity was shown by HaSCP-2 and SCP-2 inhibitors (SCPIs) could havethe potential to inhibit the biological activity of HaSCP-2. In vivo Biologicalassays reveled that SCPI-treated larvae at young stage showed a significantdecrease of cholesterol uptake. This novel study thus represent an outstanding effort toelucidate the NMR structure of SCP-2 in H. armigera and revealed itsimportant function in cholesterol uptake which paved theway for designing of potent environmentallyfriendly pesticides exploiting SCP-2with greater efficacy.