(NAS Colloquium) Virulence and Defense in Host--Pathogen Interactions Common Features Between Plants and Animals (2001) / Chapter Skim
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Structure and Function of Pectic Enzymes: Virulence Factors of Plant Pathogens
Structure and Function of Pectic Enzymes: Virulence Factors of Plant Pathogens
Pages 11-18
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From page 11... ...
The structural results have also provided the first atomic description of a pectate fragment, which differs considerably from the popular view in conformation as well as the mode of interactions with Ca2+ ions. Finally, the growing structural database of pectolytic enzymes is enabling researchers to elucidate subtle structural differences that are responsible for the specific recognition of a unique oligosaccharide sequence from a heterogeneous mix in the plant cell wall.
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From page 12... ...
2, PelC catalyzes the endo- and exolytic cleavage of the a-1-4 glycosidic bond of polygalacturonic acid, generating an unsaturated trimer end product (25~. Ca2+ is essential for the in vitro reaction and is likely required in the in vivo reaction in the plant cell wall in which the Ca2+ concentration is estimated to be as high as 1.0 mM.
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From page 13... ...
The superfamily includes 14 extracellular pectate lyases, 7 pectin lyases, and 12 plant pollen and style proteins. The corrected sequence alignment has identified 10 invariant amino acids, 5 of which are amino acids that could potentially be involved in catalytic activity.
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From page 14... ...
Structure of the PelC R218K-(Ca2+~4-pentaGalpA Complex With the active site of PelC now identified, attention has turned toward the elucidation of the atomic details of the proteinsaccharide interactions in the substrate binding site and the details of the enzymatic mechanism. In an ideal world, a crystallographer prefers to study the structure of a complex between a native protein and a transition state analogue or an inhibitor, to work out atomic details of the active site of the enzyme.
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From page 15... ...
Analogous differences are found in three-dimensional models constructed from the sequences of other pectate lyase isozymes. Thus, polygalacturonic acid may serve as a suitable in vitro substrate for all isozymes because the saccharide binding pockets near the active site recognize only galacturonic acid moieties.
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From page 16... ...
The structural results have also provided the first atomic description of a pectate fragment, finding the conformation as well as the mode of interactions with Ca2+ ions to be considerably different from the popular view. The growing structural databases of pectolytic enzymes should allow researchers to elucidate the structural motifs that recognize specific types of saccharides.
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From page 17... ...
Large scale cultivation of transformants producing mutant PLB was performed pH as outlined (43) in multiple 300 milliliter batches in one liter optimum Erlenmeyer flasks incubated in an orbital shaker (250 revolu tions per minute)
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From page 18... ...
30. Morris, E
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