Structure and function of endoglucanase V

Abstract

Cellulose is the major polysaccharide component of plant cell walls and is the most abundant organic compound on the planet. A number of bacterial and fungal organisms can use cellulose as a food source, possessing cellulases (cellobiohydrolases and endoglucanases) that can catalyse the hydrolysis of the beta-(1,4) glycosidic bonds. They can be classified into seven distinct families. The three-dimensional structures of members of two of these families are known. Here we report the structure of a third cellulase, endoglucanase V, whose sequence is not represented in any of the above families. The enzyme is structurally distinct from the previously determined cellulases but is similar to a recently characterized plant defence protein. The active site region resembles that of lysozyme, despite the lack of structural similarity between these two enzymes.

Structure determination and refinement of the Humicola insolens endoglucanase V at 1.5 Å Resolution

“…Thus far, structures of the catalytic domains of cellulases and xylanases from seven of the families have been published: cellobiohydrolase II (CBH-II) from Trichoderma reesei (Rouvinen, Bergfors, Teeri, Knowles & Jones, 1990) and endocellulase E2 from Thermomonospora fusca (Spezio, Wilson & Karplus, 1993), both from family 6; CelA from Clostridium thermocellum (Juy et al, 1992) a representative of family 9; the endoglucanase V from H. insolens (this paper and, Davies et al, 1993) from family 45; cellobiohydrolase I (CBH-I) from T. reesei (Divne et al, 1994), family 7; a number of family 11 xylanases (Campbell et al, 1993;Wakarchuk, Campbell, Sung, Davoodi & Yaguchi, 1994;TOrr/Snen, Harkki & Rouvinen, 1994); the family 10 xylanases (Derewenda et al, 1994;Harris et al, 1994;White, Withers, Gilkes & Rose, 1994) and most recently CelCCA, a cellulase from family 5 (Ducros et al, 1996). Although all of these structures facilitate catalysis via a similar acid/base mechanism involving two or more aspartate or glutamate residues (for reviews on these mechanisms of catalysis see Koshland, 1953;Sinnott, 1990, McCarter & Withers, 1994, the structures of the cellulases from each family may be quite distinct.…”

“…We have determined the structure of the 210-residue catalytic core domain of the endoglucanase V (EGV) from H. insolens at 1.5 A, resolution (Davies et al, 1993). EGV is a cellulase from family 45 which includes the 43 kDa endocellulase B from Pseudomonasfluorescens (Gilbert, Hall, Hazlewood & Ferreira, 1990), the EGV from T. reesei (Saloheimo, Henrissat, Hoffrrn, Teleman, & Penttil~i, 1994) and the EGV from Fusarium oxysporum (Sheppard et al, 1994).…”

Dynamic light scattering study of the two‐domain structure of Humicola insolens endoglucanase V

“…It has long been noted that removal of the cellulosebir~ding domain from a two-domain cellulase dramatically reduces the activity of the truncated enzyme on microcrystalline cellulose [1,2,5] and this has led to suggest that the spatial arrangement of the two constitutive domains would be essential for optimal activity. The three-dimensional structures of a n umbe:" of isolated cellulase catalytic domains [6][7][8][9][10][11][12] and of cellulo,e-binding domains [13,14] have been determined. However, it 1ms so far proven impossible to crystallize an entire cellulase, i.e one containing the two domains.…”

Dimension, Shape, and Conformational Flexibility of a Two Domain Fungal Cellulase in Solution Probed by Small Angle X-ray Scattering

“…Cel45 has a catalytic module belonging to the glycoside hydrolase family 45 carrying a CBM of family 1 via a 36 amino acid long linker peptide (21). The three-dimensional structure of the catalytic module has been determined (22) and that of the CBM could be directly modeled from its 50% sequence identity to cellobiohydrolase I (Cel7A) from Trichoderma reesei, whose three-dimensional structure was solved by NMR (23).…”