Structure of full‐length class I chitinase from rice revealed by X‐ray crystallography and small‐angle X‐ray scattering

Abstract

The rice class I chitinase OsChia1b, also referred to as RCC2 or Cht‐2, is composed of an N‐terminal chitin‐binding domain (ChBD) and a C‐terminal catalytic domain (CatD), which are connected by a proline‐ and threonine‐rich linker peptide. Because of the ability to inhibit fungal growth, the OsChia1b gene has been used to produce transgenic plants with enhanced disease resistance. As an initial step toward elucidating the mechanism of hydrolytic action and antifungal activity, the full‐length structure of OsChia1b was analyzed by X‐ray crystallography and small‐angle X‐ray scattering (SAXS). We determined the crystal structure of full‐length OsChia1b at 2.00‐Å resolution, but there are two possibilities for a biological molecule with and without interdomain contacts. The SAXS data showed an extended structure of OsChia1b in solution compared to that in the crystal form. This extension could be caused by the conformational flexibility of the linker. A docking simulation of ChBD with tri‐N‐acetylchitotriose exhibited a similar binding mode to the one observed in the crystal structure of a two‐domain plant lectin complexed with a chitooligosaccharide. A hypothetical model based on the binding mode suggested that ChBD is unsuitable for binding to crystalline α‐chitin, which is a major component of fungal cell walls because of its collisions with the chitin chains on the flat surface of α‐chitin. This model also indicates the difference in the binding specificity of plant and bacterial ChBDs of GH19 chitinases, which contribute to antifungal activity. Proteins 2010. © 2010 Wiley‐Liss,Inc.

The Structure- and Metal-dependent Activity of Escherichia coli PgaB Provides Insight into the Partial De-N-acetylation of Poly-β-1,6-N-acetyl-d-glucosamine

“…3B). The presence of a MES molecule in the active site groove has also been observed for the chitinase Chia1b from Oryza sativa (Protein Data Bank entry 3IWR) (57).…”

The Structure of the Catalytic Domain of a Plant Cellulose Synthase and Its Assembly into Dimers

“…Examples relevant to plants include the extracellular cellulosome scaffolding structures plant cell wall digesting bacteria (Linder and Teeri, 1997;Currie et al, 2013), homo-and heterodimerization related to metal binding detoxifying proteins (Bilecen et al, 2005), pectinases-inhibitor binding interactions (Benedetti et al, 2011), and a plant hormone abscisic acid receptor (Nishimura et al, 2009). SAXS has also been used to study time-resolved structural dynamics to illustrate differences between active versus inactive states of proteins and solution properties that differ from their respective crystal structures (Lamb et al, 2009;Kezuka et al, 2010).…”

Contribution of Chitinase A’s C-Terminal Vacuolar Sorting Determinant to the Study of Soluble Protein Compartmentation

“…X-ray structures of several plant class I and II chitinases indicate a compact fold of the catalytic domain where the C -terminus is extended along the surface in such a way that additional residues would stick out over the catalytic cleft [5,6]. It is thus to be expected that the C -terminal propeptides found in many vacuolar class I chitinases are easily accessible to the sorting machinery as well as easily removed by endo- or exo-peptidases.…”