Structure-function relationships of tt and p elicitins, signal proteins involved in the plant-Phytophthora interaction

Abstract. Elicitins form a family of 10-kDa holoproteins secreted by various Phytophthora species. The large-scale purification of parasiticein, a novel elicitin secreted by P. parasitica, led to the determination of its sequence. We have compared the necrotic activities and the primary and secondary structures (determined through circular dichroism) of four elicitins. On tobacco plants, they could be classified into two classes: a, comprising capsicein and parasiticein (less necrotic), and ]3, comprising cryptogein and cinnamomin (very toxic with a necrosis threshold of 0.1 i~g per leaf). The features of elicitin structure which might be involved in the interaction of elicitins with the leaf target cells and that could explain the different necrosis-inducing properties of the two proteins are investigated. About 75% sequence identity was observed between the four elicitins: only two short terminal regions are heterologous, while the central core is mainly conserved. The circular-dichroism spectra showed that the secondary structure of the elicitins was largely conserved. All of them consisted of approx. 50% a-helix with little or no [3-structure. Comparisons of the complete sequences, amino-acid compositions, isoelectric points, hydropathy indices and th e secondary-structure predictions correlated with the necrotic classification. Alpha elicitins corresponded to acidic molecules with a valine residue at position 13, while 13 elicitins were basic with a lysine at this position, which appeared to be a putative active site responsible for necrosis induction

Human genetic polymorphisms in T1R1 and T1R3 taste receptor subunits affect their function.

International audienceUmami is the typical taste induced by monosodium glutamate (MSG), which is thought to be detected by the heterodimeric G protein-coupled receptor, T1R1 and T1R3. Previously, we showed that MSG detection thresholds differ substantially between individuals and we further showed that nontaster and hypotaster subjects are associated with nonsynonymous single polymorphisms occurring in the T1R1 and T1R3 genes. Here, we show using functional expression that both amino acid substitutions (A110V and R507Q) in the N-terminal ligand-binding domain of T1R1 and the 2 other ones (F749S and R757C), located in the transmembrane domain of T1R3, severely impair in vitro T1R1/T1R3 response to MSG. A molecular model of the ligand-binding region of T1R1/T1R3 provides a mechanistic explanation supporting functional expression data. The data presented here support causal relations between the genotype and previous in vivo psychophysical studies in human evaluating sensitivity to MSG

Caracterisation de la prise d'oxygene a la lumiere chez deux vegetaux modeles : influence d'un regulateur de croissance sur les echanges gazeux

SIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Identification of a lysyl residue defining the binding specificity of a human odorant-binding protein

International audienc

Relationships between the structure, the movement and the toxicity of alpha and beta elicitins secreted by Phytophthora sp.

National audienc

Identification of a lysyl residue defining the binding specificity of a human odorant-binding protein

International audienc

Identification par mutagenèse dirigée et synthèse peptidique du site toxique majeur des élicitines, éliciteurs des défenses des plantes sécrétés par les champignons phytopathogènes Phythophthora

National audienc

An original method of ligand binding study applied to a novel heterologous rat odorant-binding protein variant

Événement(s) lié(s) : - 14. European Chemoreception Research Organisation Congress ECRO; Brighton (GBR) - (2000-07-20 - 2000-07-24)International audienc

Conformational change of the rat odorant-binding protein OBP-1F upon odorant binding

National audienc

Mapping the elicitor and necrotic sites of Phytophthora elicitins with synthetic peptides and reporter genes controlled by tobacco defense gene promoters

International audienc