Rhamnogalacturonan I (RG-I) is a structurally complex pectic polysaccharide that is present in the cell walls of all vascular plants. Due to its structural complexity, little is known about RG-I structural diversity in different cells, tissues, and species, or about how it interacts with cellulose and other glycopolymers to regulate the properties and functions of the plant cell wall. To gain insight into structure-function relationships of pectin in the cell wall, the development of new methods for the assessment of RG-I fine structure is crucial.
Enzymatic toolbox for linkage-specific deconstruction of RG-I to study side chain structure and patterning
We are identifying new enzymes found in gut bacteria that are able to break down different portions of the RG-I molecule in order to obtain simpler fragments that can then be studied using analytical methods.
Development of Chemical and Spectroscopic Methods for Structural Characterization of RG-I
Christian Heiss, Li Tan, Parastoo Azadi
The different polysaccharides making up plant cell walls vary in their solubility, and even a single type of polysaccharide can be more or less soluble depending on how tightly it is associated with other cell wall components. We are developing new methods – using both nuclear magnetic resonance spectroscopy and mass spectrometry – that are aimed at solubilizing all of the cell wall polysaccharides together, so that we can obtain a comprehensive picture of polysaccharide composition and structure.
Biosynthesis and Function of RG-I
To further our understanding of RG-I biosynthesis and function, we are using the robust HEK293 cell heterologous protein expression system developed at the CCRC to express functional plant cell wall glycosyltransferases (GTs) and GT complexes to study how RG-I synthesis is initiated, the mechanism of RG-I backbone elongation, and the identity and characteristics of enzymes that add the glycosyl and non-glycosyl substituents onto the backbone.