A project led by Riddet Institute Researchers Professor Jameson and Professor Williams was awarded $935,000 by the Royal Society Te Apārangi annual Marsden Fund this week.
The project, “Pectin methylesterases: tuning pectin function with complex variations upon a simple theme”, will look at an important structural component of plant cells in the hopes of creating 'designer' pectins with potential applications across biotechnology. The project will be led by Professor Geoff Jameson and Professor Bill Williams, who are principal and associate investigators in the Riddet Institute, respectively. They will work alongside Professor Brett Savary of Arkansas State University, Professor Jérôme Pelloux, Université de Picardie Jules Verne, and Dr Davide Mercadante, University of Zürich. Dr Mercadante was a Riddet-funded PhD scholar 2009-2012 in a two-University collaboration (supervised by Riddet Institute Investigator-Laureate, Professor Melton at the University of Auckland and by Bill Williams and Geoff Jameson at Massey University. This project builds on work he undertook during his PhD.
Pectin, a complex polysaccharide well known for making jams and jellies, is an important structural component of plant cell walls. There is a large family of enzymes called pectin methylesterases (PMEs) within the plant cell wall, which modify pectin throughout the plant’s life-cycle. The team seek to uncover the mechanism by which PME do this and thereby to make 'designer' pectins with potential applications across biotechnology.
However, Professor Jameson says, “Unfortunately, we understand remarkably little of how PMEs work. Despite sharing a common scaffold amongst plants, fungi and bacteria, these enzymes show widely varying preferences in conditions of temperature, pH and salt for best activity. We have made the first detailed characterisation of a non-processive fungal PME. These results provide the foundation for our studies on a range of PMEs (and mutants) to uncover the mechanism.”
And Professor Williams adds, “Whereas some PMEs hydrolyse methylester groups of pectin in a processive manner, a kind of molecular motor mower, creating long blocks of negatively charged carboxylate groups, others operate non-processively, as a kind of randomly-grazing molecular moa. Our recent molecular-dynamics simulations for a processive bacterial PME revealed that for a specifically patterned pectin the pectin-PME system behaved as a novel Brownian-ratchet molecular motor.”
The group will apply state-of-the-art biophysical techniques ranging from optical tweezers on single molecules, allowing first-ever studies to be undertaken on the response of PME to stretching of pectin as may be encountered in plant cell walls, to X-ray diffraction to uncover how nature tunes pectin structure and function.