Structure and Properties of a Non-processive, Salt-requiring, and Acidophilic Pectin Methylesterase from Aspergillus niger Provide Insights into the Key Determinants of Processivity Control.
Primary Citation of Related Structures: 5C1C, 5C1E
PubMed Abstract:
Many pectin methylesterases (PMEs) are expressed in plants to modify plant cell-wall pectins for various physiological roles. These pectins are also attacked by PMEs from phytopathogens and phytophagous insects. The de-methylesterification by PMEs of the O6-methyl ester groups of the homogalacturonan component of pectin, exposing galacturonic acids, can occur processively or non-processively, respectively, describing sequential versus single de-methylesterification events occurring before enzyme-substrate dissociation ...
Many pectin methylesterases (PMEs) are expressed in plants to modify plant cell-wall pectins for various physiological roles. These pectins are also attacked by PMEs from phytopathogens and phytophagous insects. The de-methylesterification by PMEs of the O6-methyl ester groups of the homogalacturonan component of pectin, exposing galacturonic acids, can occur processively or non-processively, respectively, describing sequential versus single de-methylesterification events occurring before enzyme-substrate dissociation. The high resolution x-ray structures of a PME from Aspergillus niger in deglycosylated and Asn-linked N-acetylglucosamine-stub forms reveal a 10⅔-turn parallel β-helix (similar to but with less extensive loops than bacterial, plant, and insect PMEs). Capillary electrophoresis shows that this PME is non-processive, halophilic, and acidophilic. Molecular dynamics simulations and electrostatic potential calculations reveal very different behavior and properties compared with processive PMEs. Specifically, uncorrelated rotations are observed about the glycosidic bonds of a partially de-methyl-esterified decasaccharide model substrate, in sharp contrast to the correlated rotations of processive PMEs, and the substrate-binding groove is negatively not positively charged.
Related Citations:
Processive pectin methylesterases: the role of electrostatic potential, breathing motions and bond cleavage in the rectification of Brownian motions Mercadante, D., Melton, L.D., Jameson, G.B., Williams, M.A.K. (2014) PLoS One 9: e87581
Substrate Dynamics in Enzyme Action: Rotations of Monosaccharide Subunits in the Binding Groove are Essential for Pectin Methylesterase Processivity Mercadante, D., Melton, L.D., Jameson, G.B., Williams, M.A.K., De Simone, A. (2013) Biophys J 104: 1731
Organizational Affiliation:
From Riddet Institute and Institute of Fundamental Sciences, Massey University, Palmerston North 4442, New Zealand, MacDiarmid Institute for Advanced Materials and Nanotechnology, Palmerston North 4442, New Zealand g.b.jameson@massey.ac.nz.
Download Mendeley
