Structure-function analysis of a broad specificity Populus trichocarpa endo-β-glucanase reveals an evolutionary link between bacterial licheninases and plant XTH gene products

• The large xyloglucan endotransglycosylase/hydrolase (XTH) gene family continues to be the focus of much attention in studies of plant cell wall morphogenesis due to the unique catalytic functions of the enzymes it encodes. The XTH gene products compose a subfamily of glycoside hydrolase family 16 (GH16), which also comprises a broad range of microbial endoglucanases and endogalactanases, as well as yeast cell wall chitin/β-glucan transglycosylases. Previous whole-family phylogenetic analyses have suggested that the closest relatives to the XTH gene products are the bacterial licheninases (EC 3.2.1.73), which specifically hydrolyze linear mixed linkage β(1→3)/β(1→4)-glucans. In addition to their specificity for the highly branched xyloglucan polysaccharide, XTH gene products are distinguished from the licheninases and other GH16 enzyme subfamilies by significant active site loop alterations and a large C-terminal extension. Given these differences, the molecular evolution of the XTH gene products in GH16 has remained enigmatic. Here, we present the biochemical and structural analysis of a unique, mixed function endoglucanase from black cottonwood (Populus trichocarpa), which reveals a small, newly recognized subfamily of GH16 members intermediate between the bacterial licheninases and plant XTH gene products. We postulate that this clade comprises an important link in the evolution of the large plant XTH gene families from a putative microbial ancestor. As such, this analysis provides new insights into the diversification of GH16 and further unites the apparently disparate members of this important family of proteins.

Ämnesord

NATURVETENSKAP  -- Biologi -- Biokemi och molekylärbiologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Biochemistry and Molecular Biology (hsv//eng)

Nyckelord

Broad specificities

C-terminal extensions

Catalytic functions

Glycoside hydrolase family 16

Molecular evolution

Phylogenetic analysis

Populus trichocarpa

Structure-function analysis

Catalysis

Enzyme activity

Molecular biology

Plant cell culture

Plants (botany)

Polymers

Genes

bacterial enzyme

endo beta glucanase

glucan synthase

licheninase

unclassified drug

article

cladistics

enzyme specificity

enzyme structure

multigene family

nucleotide sequence

plant gene

priority journal

structure activity relation

XTH gene

Carbohydrate Processing

Cellulase

Enzyme Kinetics

Glycoside Hydrolases

Plant Cell Wall

Polysaccharide

Xyloglucan

Xyloglucan Endotransglycosylase/Hydrolase (XTH)

Bacterial Proteins

Catalytic Domain

Evolution

Molecular

Glycosyltransferases

Phylogeny

Plant Proteins

Populus

Protein Structure

Secondary

Publikations- och innehållstyp

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