Article Figures & Data
Figures
- Fig. 1.
Top, Examples of modular glycoside hydrolases and related proteins. The yellow boxes represent the catalytic domain with the glycoside hydrolase family number indicated after GH. The function of the protein is indicated in parentheses where it was experimentally determined. Carbohydrate-binding modules are shown in blue with the family number appearing after CBM, gray boxes labeled UNK represent regions of unknown function, black boxes labeled TM represent transmembrane segments, other modules are indicated by their function (esterase) or name (dockerin; FN3, fibronectin type III-like), and pink boxes labeled X8 represent a newly identified module family found in plants (see text). When two consecutive modules are separated by a clearly identifiable linker peptide, the peptide is indicated by a horizontal line. Bottom, Multiple sequence alignment of Chrk1 with selected family GH18 members: chitinase V of tobacco (Nicotiana tabacum; Q43591);Serratia marcescens chitinase A (P07254); Hevea brasiliensis chitinase (hevamine; P23472); and concanavalin B ofCanavalia ensiformis (P49347). Similarities are outlined in gray; the secondary structure (b for strand, a for helix) found in the three-dimensional structures of the chitinases from S. marcescens, H. brasiliensis, and concanavalin B are indicated under each sequence. The catalytic residue of chitinases is noted in white on a black background.
- Fig. 2.
Examples of modular glycosyltransferases and related proteins. Pale-green boxes represent the catalytic domain with the glycosyltransferase family number indicated after GT, carbohydrate-binding modules are shown in blue with the family number appearing after CBM, gray boxes labeled UNK represent regions of unknown function, the yellow box represent a module belonging to glycoside hydrolase family GH17, and the pink boxes on the last line represent tetratricopeptide repeats. Other modules are indicated by their putative function (myosin motor and esterase). Several chitin synthases bear an N-terminal myosin motor protein and this strongly suggests that chitin synthesis may be guided by association with cytoskeletal structures (Fujiwara et al., 1997).
- Fig. 3.
A, Modeled structure of ORF T27I1.7 from Arabidopsis (O80596), which consists of four repeats of a CBM22 module (homologs are implicated in xylan binding; Charnock et al., 2000), together with a family GH10 xylanase catalytic domain (Fig. 1). B, Modeled structure for a putative plant oligosaccharide receptor. ORF Chrk1 from tobacco (Q9SWX8) displays an extracellular domain with homology to family GH-18 chitinases, but lacks the essential catalytic acid residue. This domain is linked via a transmembrane segment to a Ser/Thr kinase domain. This allows us to propose a model for oligosaccharide signaling events in plants. These figures were drawn with the MOLSCRIPT program (Kraulis, 1991) using Protein Data Bank entries with accession numbers 1DYO and 1EOW (A) and 1CTNand 3LCK (B).
