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| - | [[Image:1buq.jpg|left|200px]] | + | {{Seed}} |
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| | {{STRUCTURE_1buq| PDB=1buq | SCENE= }} | | {{STRUCTURE_1buq| PDB=1buq | SCENE= }} |
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| - | '''SOLUTION STRUCTURE OF DELTA-5-3-KETOSTEROID ISOMERASE COMPLEXED WITH THE STEROID 19-NORTESTOSTERONE-HEMISUCCINATE'''
| + | ===SOLUTION STRUCTURE OF DELTA-5-3-KETOSTEROID ISOMERASE COMPLEXED WITH THE STEROID 19-NORTESTOSTERONE-HEMISUCCINATE=== |
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| - | ==Overview==
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| - | The solution structure of the ketosteroid isomerase homodimer complexed with the product analogue 19-nortestosterone hemisuccinate (19-NTHS) was solved by heteronuclear multidimensional NMR methods using 1647 distance restraints, 77 dihedral angle (phi) restraints, and 67 hydrogen bond restraints per monomer. The refined secondary structure of each subunit consists of three alpha-helices, eight beta-strands, four turns, and two beta-bulges. The beta-strands form a mixed beta-sheet. One of the five proline residues, Pro-39, is cis and begins a nonclassical turn. A self-consistent ensemble of 15 tertiary/quaternary structures of the enzyme dimer-steroid complex, with no distance violations greater than 0.35 A, was generated by simulated annealing and energy minimization with the program X-PLOR. The mean pairwise RMSD of the secondary structural elements was 0.63 A for the average subunit and 1.25 A for the dimer. Within each subunit, the three alpha-helices are packed onto the concave surface of the beta-sheet with a groove between them into which the steroid binds at a site defined by 14 intermolecular distances. In the productive complex, Tyr-14, from alpha-helix 1, approaches both Asp-99 and the 3-keto group of 19-NTHS while, from beta-strand 1, the carboxylate of Asp-38 approaches the beta-face of the steroid near C4 and C6, between which it transfers a proton during catalysis. Thus the solution structure of the isomerase-steroid complex can accommodate the catalytic diad mechanism in which Asp-99 donates a hydrogen bond to Tyr-14 which in turn is hydrogen bonded to the 3-oxygen of the steroid. While direct hydrogen bonding of Asp-99 to the steroid oxygen is less likely, it cannot be excluded. All other interactions of the steroid with the enzyme are hydrophobic. The dimer interface, which is between the convex surfaces of the beta-sheets, is defined by 28 intersubunit NOEs between hydrophobic residues in the 13C-filtered NOESY-HSQC spectrum of a 13C/12C-heterolabeled dimer. Both hydrophobic and polar interactions occur at the dimer interface which contains no space that would permit additional steroid binding. Comparison of the complexed enzyme with the solution structure of the free enzyme [Wu et al. (1997) Science 276, 415-418] reveals that the three helices change position in the steroid complex, becoming more closely packed onto the concave surface of the beta-sheet, thus bringing Tyr-14 closer to Asp-99 and the substrate. Comparison of the enzyme-steroid complex in solution with the free enzyme in the crystalline state reveals similar differences between the positions of the helices.
| + | The line below this paragraph, {{ABSTRACT_PUBMED_9778345}}, adds the Publication Abstract to the page |
| | + | (as it appears on PubMed at http://www.pubmed.gov), where 9778345 is the PubMed ID number. |
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| | + | {{ABSTRACT_PUBMED_9778345}} |
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| | ==About this Structure== | | ==About this Structure== |
| - | 1BUQ is a [[Single protein]] structure of sequence from [http://en.wikipedia.org/wiki/Comamonas_testosteroni Comamonas testosteroni]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1BUQ OCA]. | + | 1BUQ is a [[Single protein]] structure of sequence from [http://en.wikipedia.org/wiki/Comamonas_testosteroni Comamonas testosteroni]. Full experimental information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1BUQ OCA]. |
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| | ==Reference== | | ==Reference== |
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| | [[Category: Enzyme]] | | [[Category: Enzyme]] |
| | [[Category: Ketosteroid isomerase-19nth]] | | [[Category: Ketosteroid isomerase-19nth]] |
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 11:58:43 2008'' | + | |
| | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jun 30 19:45:00 2008'' |
Revision as of 16:45, 30 June 2008
Template:STRUCTURE 1buq
SOLUTION STRUCTURE OF DELTA-5-3-KETOSTEROID ISOMERASE COMPLEXED WITH THE STEROID 19-NORTESTOSTERONE-HEMISUCCINATE
Template:ABSTRACT PUBMED 9778345
About this Structure
1BUQ is a Single protein structure of sequence from Comamonas testosteroni. Full experimental information is available from OCA.
Reference
Solution structure of Delta 5-3-ketosteroid isomerase complexed with the steroid 19-nortestosterone hemisuccinate., Massiah MA, Abeygunawardana C, Gittis AG, Mildvan AS, Biochemistry. 1998 Oct 20;37(42):14701-12. PMID:9778345
Page seeded by OCA on Mon Jun 30 19:45:00 2008
