Structural analysis of the Rhizoctonia solani agglutinin reveals a domain‐swapping dimeric assembly

Abstract

Rhizoctonia solani agglutinin (RSA) is a 15.5-kDa lectin accumulated in the mycelium and sclerotia of the soil born plant pathogenic fungus R. solani. Although it is considered to serve as a storage protein and is implicated in fungal insecticidal activity, its physiological role remains unclear as a result of a lack of any structure/function relationship information. Glycan arrays showed that RSA displays high selectivity towards terminal nonreducing N-acetylgalactosamine residues. We determined the amino acid sequence of RSA and also determined the crystal structures of the free form and the RSA-N-acetylgalactosamine complex at 1.6 and 2.2 A resolution, respectively. RSA is a homodimer comprised of two monomers adopting the b-trefoil fold. Each monomer accommodates two different carbohydrate-binding sites in an asymmetric way. Despite RSA topology similarities with R-type lectins, the two-monomer assembly involves an N-terminal swap, thus creating a dimer association novel to R-type lectins. Structural characterization of the two carbohydrate-binding sites offers insights on the structural determinants of the RSA carbohydrate specificity.

Suppression subtractive hybridization and comparative expression of a pore-forming toxin and glycosyl hydrolase genes in Rhizoctonia solani during potato sprout infection

“…In accordance with our study, fungal lectins have been previously detected in the mycelium and sclerotia of R. solani strains of different anastomosis groups (Kellens and Peumans 1991;Mghalu et al 2004) with a reported role in fungal growth and development (Leonidas et al 2007). Additionally, R. solani lectins were revealed to act as storage proteins (Skamnaki et al 2013). The down-regulation of R. solani AG-3 Rs114 lectins Fig.…”

Entomotoxic and nematotoxic lectins and protease inhibitors from fungal fruiting bodies

“…Homodimer 4 Gal na Entomotoxic (Hamshou et al 2013;Hamshou et al 2010b;Hamshou et al 2012;Skamnaki et al 2013) Bleuler-Martinez et al 2011;Fujihashi et al 2003;Fukumori et al 1990;Kochibe and Furukawa 1980;Olausson et al 2010;Olausson et al 2008;Tateno et al 2009;Wimmerova et al 2003) GlcNAc-β1,4-X na nd (Cioci et al 2006;Ueda et al 1999a;Ueda et al 2002;Ueda et al 1999b;Ueda et al 2003) Entomotoxic (Birck et al 2004;Bleuler-Martinez et al 2011;Damian et al 2005;Francis et al 2003;Jaber et al 2008;Jaber et al 2007;…”

“…While galectins bind linear glycans in a groove parallel to the protein surface, β-trefoil-type lectins bind them in a perpendicular orientation, in which only the non-reducing end of the glycan interacts with the binding pocket. All these proteins assemble to homodimers but, interestingly, each protein uses a different interface for dimer formation (Bovi et al 2013;Pohleven et al 2012;Schubert et al 2012;Skamnaki et al 2013;Sulzenbacher et al 2010;Žurga et al 2014).…”

Identification of mycoparasitism-related genes against the phytopathogen Sclerotinia sclerotiorum through transcriptome and expression profile analysis in Trichoderma harzianum

“…Their expression observed in our study suggests a possible role in mycoparasitism, complementing the classical GH activity which is known to be involved. The carbohydrate binding module Family 13 gene encodes a protein with a domain related to lectins, which, in Rhizoctonia solani , is implicated in fungal insecticidal activity [33]. Our expression data suggest that this gene is related to the lectins and may play a role mediating the physical contact with the host and elicitation of the signaling cascade comprising G-proteins and MAPKs.…”