Structural features conferring dual Geranyl/Farnesyl diphosphate synthase activity to an aphid prenyltransferase

• Published in: Insect biochemistry and molecular biology Vol. 39; no. 10; pp. 707 - 716
• Main Authors: Vandermoten, Sophie, Santini, Sébastien, Haubruge, Éric, Heuze, Fabien, Francis, Frédéric, Brasseur, Robert, Cusson, Michel, Charloteaux, Benoit
• Format: Journal Article Web Resource
• Language: English
• Published: England Elsevier Ltd 01.10.2009; Pergamon Press (part of Elsevier Science)
• Subjects: Acyrthosiphon pisum; amino acid sequences; Animals; Aphid; Aphididae; Aphids - chemistry; Aphids - enzymology; Aphids - genetics; biochemical pathways; chemical structure; Dimethylallyltranstransferase - chemistry; Dimethylallyltranstransferase - genetics; Dimethylallyltranstransferase - metabolism; Diphosphates - metabolism; Diterpenes - metabolism; Entomologie & lutte antiravageur; Entomology & pest control; enzyme activity; enzyme inhibition; enzyme substrates; enzymes; geranyl diphosphate/farnesyl diphosphate synthase; Geranyltranstransferase - chemistry; Geranyltranstransferase - genetics; Geranyltranstransferase - metabolism; Homology modelling; hydrogen bonding; insect pests; insect pheromones; Isoprenyl diphosphate synthase; isoprenyl diphosphate synthases; juvenile hormones; Life sciences; mechanism of action; Models, Molecular; Molecular dynamics; molecular sequence data; mutants; Mutation; nucleotide sequences; Pheromone and juvenile hormone biosynthesis; plant pests; Polyisoprenyl Phosphates - metabolism; protein prenylation; salt bridges; Sciences du vivant; Sesquiterpenes - metabolism; Substrate Specificity; terpenoids; GGPP; GPP; FPP; Molecular dynamics; scIPPS; IPP; RMSF; Isoprenyl diphosphate synthase; RMSD; FPPS; GPPS; ApIPPS; FARM; GGPPS; DMAPP; CLD; Pheromone and juvenile hormone biosynthesis; Aphid; Homology modelling; MpIPPS
• ISSN: 0965-1748; 1879-0240; 1879-0240
• DOI: 10.1016/j.ibmb.2009.08.007

In addition to providing lipid chains for protein prenylation, short-chain isoprenyl diphosphate synthases (scIPPSs) play a pivotal role in the biosynthesis of numerous mevalonate pathway end-products, including insect juvenile hormone and terpenoid pheromones. For this reason, they are being considered as targets for pesticide development. Recently, we characterized an aphid scIPPS displaying dual geranyl diphosphate (GPP; C 10)/farnesyl diphosphate (FPP; C 15) synthase activity in vitro. To identify the mechanism(s) responsible for this dual activity, we assessed the product selectivity of aphid scIPPSs bearing mutations at Gln107 and/or Leu110, the fourth and first residue upstream from the “first aspartate-rich motif” (FARM), respectively. All but one resulted in significant changes in product chain-length selectivity, effectively increasing the production of either GPP (Q107E, L110W) or FPP (Q107F, Q107F–L110A); the other mutation (L110A) abolished activity. Although some of these effects could be attributed to changes in steric hindrance within the catalytic cavity, molecular dynamics simulations identified other contributing factors, including residue-ligand Van der Waals interactions and the formation of hydrogen bonds or salt bridges between Gln107 and other residues across the catalytic cavity, which constitutes a novel product chain-length determination mechanism for scIPPSs. Thus the aphid enzyme apparently evolved to maintain the capacity to produce both GPP and FPP through a balance between these mechanisms.