Project leaders: Prof. Tuula Teeri
Prof. Geoffrey Daniel

Carbohydrate binding modules as analytical tools for mapping pulp fibre surfaces

Aim: The aim of the project is to develop novel analytical tools based on carbohydrate binding modules (CBMs) for investigate the carbohydrate composition and spatial distribution on pulp fibre surfaces.

Background: Enzymes involved in carbohydrate metabolism and turnover often have modular structures with a catalytic domain linked to one or more substrate-binding modules. The first CBMs isolated showed affinity towards cellulose. Later on other CBMs have been found, with affinity towards other cell wall carbohydrates such as xylan, chitin and mannan. Since these are recognition elements evolved in nature, their specificity is better than for example that of antibodies generated against carbohydrates, which are often poorly antigenic.

Project description: Different CBMs are expressed in E. coli, fused to the engineered double ZZ-domain of the staphylococcal protein A. The ZZ-domain provides a specific binding site of antibodies and thus allows direct immunogold labeling of the fusion proteins (see Fig 1). Since no secondary antibodies are needed, better resolution can be achieved when transmisson electron microscopy (TEMI is used for imaging). When CBMs with different specificities are fused to the ZZ-module, the different carbohydrates located on pulp fibre surfaces can be mapped with very good precision. The project involves cloning and expression of CBMs with known substrate specificity as well as the characterization of CBMs with so far unknown binding specificity. 

Figure 1. The principle of carbohydrate mapping of fibre surfaces using the CBM-fusion proteins

Project group:
Professor Tuula Teeri, Ph.D. student Åsa Kallas, Department of Biotechnology, Royal Institute of Technology, AlbaNova University Centre, 106 91 Stockholm, Sweden.

Professor Geoffrey Daniel, Lada Filonova, Wood Ultrastructure Research Centre (WURC), Dept. Wood Science, Swedish University of Agricultural Sciences, Box 7008, 750 07 Uppsala