High‐affinity binding of a synthetic heptaglucoside and fungal glucan phytoalexin elicitors to soybean membranes

FEBS Letters

van Boom, Jacques²  Ebel, Jürgen¹  Frey, Thomas¹  Verduyn, Richard²  Cosio, Eric G.¹ 

[1] Lehrstuhl für Biochemie der Pflanzen, Biologisches Institut II der Universität, Schänzlestr. 1, D-7800 Freiburg FRG;Gorlaeus Laboratories, Leiden University, PO Box 9502, NL-2300 RA Leiden, The Netherlands

关键词: Heptaglucoside;    Membrane;    Phytoalexin elicitor;    Receptor;    APEA;    2-(4-aminophenyl)ethylamine;    DP;    degree of polymerization;    HG-APEA;    1-[2-(4-aminophenyl)ethyl]amino-1-[hexaglucosyl]deoxyglucitol;    Pmg;    Phytophthora megasperma f.sp. glycinea;   

DOI  :  10.1016/0014-5793(90)80411-B

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

Soybean membranes possess high-affinity binding sites for fungal β-glucans that elicit phytoalexin synthesis. The ability of 1,3-1,6-β-glucans, released by acid hydrolysis from mycelial walls of Phytophthora megasperma f.sp. glycinea, to compete for the putative phytoalexin elicitor receptors increases with their average degree of polymerization (DP). The results suggest a function where the probability for glucan fragments of containing a structural determinant that is optimal for binding approaches 1 as the DP tends to infinity. Ligand displacement data obtained against a ¹²⁵I-labeled glucan elicitor (average DP= 18) provided a theoretical minimum IC₅₀ (50% inhibitory concentration) for 1,3-1,6-β-glucans of 3 nM. The IC₅₀ value obtained for a synthetic hepta-β-glucoside having a known elicitor-active structure was 8 nM, remarkably close to the predicted value. Displacement of the ¹²⁵I-glucan of large DP was uniform and complete showing that the heptaglucoside had access, with similar affinity, to all sites available to the radioligand. Further analysis using a ¹²⁵I-labeled aminophenethylamine derivative of the heptaglucoside suggested that the putative glucan-elicitor receptors bind a basic structural determinant present in all elicitor-active glucans from the soybean pathogen P. megasperma.

【 授权许可】

Unknown