1e4b: Difference between revisions
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==Overview== | ==Overview== | ||
The crystal structures of l-fuculose-1-phosphate aldolase (FucA) with and, without a ligated analogue of dihydroxyacetone phosphate (DHAP) and of a, number of active center mutants have resulted in a model of the catalytic, mechanism. This model has now been confirmed by structural analyses of, further mutations at the zinc coordination sphere and at the phosphate, site. In addition, these mutants have revealed new aspects of the, catalysis: the hydroxyl group of Tyr113' (from a neighboring subunit), which sits just outside the zinc coordination sphere, steers DHAP towards, a productive binding mode at the zinc ion; Glu73 contacts zinc in between, the two ligand positions intended for the DHAP oxygen atoms and thus, avoids blocking of these positions by a tetrahedrally coordinated .. | The crystal structures of l-fuculose-1-phosphate aldolase (FucA) with and, without a ligated analogue of dihydroxyacetone phosphate (DHAP) and of a, number of active center mutants have resulted in a model of the catalytic, mechanism. This model has now been confirmed by structural analyses of, further mutations at the zinc coordination sphere and at the phosphate, site. In addition, these mutants have revealed new aspects of the, catalysis: the hydroxyl group of Tyr113' (from a neighboring subunit), which sits just outside the zinc coordination sphere, steers DHAP towards, a productive binding mode at the zinc ion; Glu73 contacts zinc in between, the two ligand positions intended for the DHAP oxygen atoms and thus, avoids blocking of these positions by a tetrahedrally coordinated hydroxy, ion; the FucA polypeptide does not assume its minimum energy state but, oscillates between two states of elevated energy as demonstrated by a, mutant in a minimum energy state. The back and forth motion involves a, mobile loop connecting the phosphate site with intersubunit motions and, thus with the Brownian motion of the solvent. The phosphate group is bound, strongly at a given distance to the zinc ion, which prevents the formation, of too tight a DHAP:zinc complex. This observation explains our failure to, find mutants that accept phosphate-free substitutes for DHAP. The FucA, zinc coordination sphere is compared with that of carbonic anhydrase. | ||
==About this Structure== | ==About this Structure== | ||
1E4B is a | 1E4B is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli] with SO4, ZN and BME as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/L-fuculose-phosphate_aldolase L-fuculose-phosphate aldolase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=4.1.2.17 4.1.2.17] Structure known Active Sites: ACT and MUT. Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=1E4B OCA]. | ||
==Reference== | ==Reference== | ||
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[[Category: mutant structure]] | [[Category: mutant structure]] | ||
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