Convergent Evolution Sheds Light on the Anti-Beta-Elimination Mechanism Common to Family 1 and 10 Polysaccharide LyasesCharnock, S.J., Brown, I.E., Turkenburg, J.P., Black, G.W., Davies, G.J.
(2002) Proc.Natl.Acad.Sci.USA 99: 12067
- PubMed: 12221284
- DOI: 10.1073/pnas.182431199
- Primary Citation of Related Structures:  1GXM, 1GXN
- PubMed Abstract:
Enzyme-catalyzed beta-elimination of sugar uronic acids, exemplified by the degradation of plant cell wall pectins, plays an important role in a wide spectrum of biological processes ranging from the recycling of plant biomass through to pathogen vir ...
Enzyme-catalyzed beta-elimination of sugar uronic acids, exemplified by the degradation of plant cell wall pectins, plays an important role in a wide spectrum of biological processes ranging from the recycling of plant biomass through to pathogen virulence. The three-dimensional crystal structure of the catalytic module of a "family PL-10" polysaccharide lyase, Pel10Acm from Cellvibrio japonicus, solved at a resolution of 1.3 A, reveals a new polysaccharide lyase fold and is the first example of a polygalacturonic acid lyase that does not exhibit the "parallel beta-helix" topology. The "Michaelis" complex of an inactive mutant in association with the substrate trigalacturonate/Ca2+ reveals the catalytic machinery harnessed by this polygalacturonate lyase, which displays a stunning resemblance, presumably through convergent evolution, to the tetragalacturonic acid complex observed for a structurally unrelated polygalacturonate lyase from family PL-1. Common coordination of the -1 and +1 subsite saccharide carboxylate groups by a protein-liganded Ca2+ ion, the positioning of an arginine catalytic base in close proximity to the alpha-carbon hydrogen and numerous other conserved enzyme-substrate interactions, considered in light of mutagenesis data for both families, suggest a generic polysaccharide anti-beta-elimination mechanism.
York Structural Biology Laboratory, Department of Chemistry, University of York, Heslington, York YO10 5YW, United Kingdom.