1e4o
|
PHOSPHORYLASE RECOGNITION AND PHOSPHOROLYSIS OF ITS OLIGOSACCHARIDE SUBSTRATE: ANSWERS TO A LONG OUTSTANDING QUESTION
OverviewOverview
Phosphorylases are key enzymes of carbohydrate metabolism. Structural, studies have provided explanations for almost all features of control and, substrate recognition of phosphorylase but one question remains, unanswered. How does phosphorylase recognize and cleave an oligosaccharide, substrate? To answer this question we turned to the Escherichia coli, maltodextrin phosphorylase (MalP), a non-regulatory phosphorylase that, shares similar kinetic and catalytic properties with the mammalian, glycogen phosphorylase. The crystal structures of three, MalP-oligosaccharide complexes are reported: the binary complex of MalP, with the natural substrate, maltopentaose (G5); the binary complex with, the thio-oligosaccharide, 4-S-alpha-D-glucopyranosyl-4-thiomaltotetraose, (GSG4), both at 2.9 A resolution; and the 2.1 A resolution ternary complex, of MalP with thio-oligosaccharide and phosphate (GSG4-P). The results show, a pentasaccharide bound across the catalytic site of MalP with sugars, occupying sub-sites -1 to +4. Binding of GSG4 is identical to the natural, pentasaccharide, indicating that the inactive thio compound is a close, mimic of the natural substrate. The ternary MalP-GSG4-P complex shows the, phosphate group poised to attack the glycosidic bond and promote, phosphorolysis. In all three complexes the pentasaccharide exhibits an, altered conformation across sub-sites -1 and +1, the site of catalysis, from the preferred conformation for alpha(1-4)-linked glucosyl polymers.
About this StructureAbout this Structure
1E4O is a Single protein structure of sequence from Escherichia coli with PLP as ligand. Active as Phosphorylase, with EC number 2.4.1.1 Structure known Active Sites: PLA and PLB. Full crystallographic information is available from OCA.
ReferenceReference
Phosphorylase recognition and phosphorolysis of its oligosaccharide substrate: answers to a long outstanding question., Watson KA, McCleverty C, Geremia S, Cottaz S, Driguez H, Johnson LN, EMBO J. 1999 Sep 1;18(17):4619-32. PMID:10469642
Page seeded by OCA on Mon Nov 5 12:23:46 2007