1ho4: Difference between revisions
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{{STRUCTURE_1ho4| PDB=1ho4 | SCENE= }} | |||
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'''CRYSTAL STRUCTURE OF PYRIDOXINE 5'-PHOSPHATE SYNTHASE IN COMPLEX WITH PYRIDOXINE 5'-PHOSPHATE AND INORGANIC PHOSPHATE''' | '''CRYSTAL STRUCTURE OF PYRIDOXINE 5'-PHOSPHATE SYNTHASE IN COMPLEX WITH PYRIDOXINE 5'-PHOSPHATE AND INORGANIC PHOSPHATE''' | ||
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[[Category: Huber, R.]] | [[Category: Huber, R.]] | ||
[[Category: Laber, B.]] | [[Category: Laber, B.]] | ||
[[Category: | [[Category: Enzyme-product complex]] | ||
[[Category: | [[Category: Open-closed transition]] | ||
[[Category: | [[Category: Tim barrel]] | ||
[[Category: | [[Category: Water channel]] | ||
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 19:03:42 2008'' | |||
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on | |||
Revision as of 19:03, 2 May 2008
CRYSTAL STRUCTURE OF PYRIDOXINE 5'-PHOSPHATE SYNTHASE IN COMPLEX WITH PYRIDOXINE 5'-PHOSPHATE AND INORGANIC PHOSPHATE
OverviewOverview
BACKGROUND: Pyridoxal 5'-phosphate is the active form of vitamin B(6) that acts as an essential, ubiquitous coenzyme in amino acid metabolism. In Escherichia coli, the pathway of the de novo biosynthesis of vitamin B(6) results in the formation of pyridoxine 5'-phosphate (PNP), which can be regarded as the first synthesized B(6) vitamer. PNP synthase (commonly referred to as PdxJ) is a homooctameric enzyme that catalyzes the final step in this pathway, a complex intramolecular condensation reaction between 1-deoxy-D-xylulose-5'-phosphate and 1-amino-acetone-3-phosphate. RESULTS: The crystal structure of E. coli PNP synthase was solved by single isomorphous replacement with anomalous scattering and refined at a resolution of 2.0 A. The monomer of PNP synthase consists of one compact domain that adopts the abundant TIM barrel fold. Intersubunit contacts are mediated by three additional helices, respective to the classical TIM barrel helices, generating a tetramer of symmetric dimers with 422 symmetry. In the shared active sites of the active dimers, Arg20 is directly involved in substrate binding of the partner monomer. Furthermore, the structure of PNP synthase with its physiological products, PNP and P(i), was determined at 2.3 A resolution, which provides insight into the dynamic action of the enzyme and allows us to identify amino acids critical for enzymatic function. CONCLUSION: The high-resolution structures of the free enzyme and the enzyme-product complex of E. coli PNP synthase suggest essentials of the enzymatic mechanism. The main catalytic features are active site closure upon substrate binding by rearrangement of one C-terminal loop of the TIM barrel, charge-charge stabilization of the protonated Schiff-base intermediate, the presence of two phosphate binding sites, and a water channel that penetrates the beta barrel and allows the release of water molecules in the closed state. All related PNP synthases are predicted to fold into a similar TIM barrel pattern and have comparable active site architecture. Thus, a common mechanism can be anticipated.
About this StructureAbout this Structure
1HO4 is a Single protein structure of sequence from Escherichia coli. Full crystallographic information is available from OCA.
ReferenceReference
Structural basis for the function of pyridoxine 5'-phosphate synthase., Franco MG, Laber B, Huber R, Clausen T, Structure. 2001 Mar 7;9(3):245-53. PMID:11286891 Page seeded by OCA on Fri May 2 19:03:42 2008