1djo
From Proteopedia
(New page: 200px<br /><applet load="1djo" size="450" color="white" frame="true" align="right" spinBox="true" caption="1djo, resolution 2.00Å" /> '''CRYSTAL STRUCTURE OF...) |
|||
| Line 1: | Line 1: | ||
| - | [[Image:1djo.gif|left|200px]]<br /><applet load="1djo" size=" | + | [[Image:1djo.gif|left|200px]]<br /><applet load="1djo" size="350" color="white" frame="true" align="right" spinBox="true" |
caption="1djo, resolution 2.00Å" /> | caption="1djo, resolution 2.00Å" /> | ||
'''CRYSTAL STRUCTURE OF PSEUDOMONAS 7A GLUTAMINASE-ASPARAGINASE WITH THE INHIBITOR DONV COVALENTLY BOUND IN THE ACTIVE SITE'''<br /> | '''CRYSTAL STRUCTURE OF PSEUDOMONAS 7A GLUTAMINASE-ASPARAGINASE WITH THE INHIBITOR DONV COVALENTLY BOUND IN THE ACTIVE SITE'''<br /> | ||
==Overview== | ==Overview== | ||
| - | Pseudomonas 7A glutaminase-asparaginase (PGA) catalyzes the hydrolysis of | + | Pseudomonas 7A glutaminase-asparaginase (PGA) catalyzes the hydrolysis of D and L isomers of glutamine and asparagine. Crystals of PGA were reacted with diazo analogues of glutamine (6-diazo-5-oxo-L-norleucine, DON) and asparagine (5-diazo-4-oxo-L-norvaline, DONV), which are known inhibitors of the enzyme. The derivatized crystals remained isomorphous to native PGA crystals. Their structures were refined to crystallographic R = 0.20 and R(free) = 0.24 for PGA-DON and R = 0.19 and R = 0.23 for PGA-DONV. Difference Fourier electron density maps clearly showed that both DON and DONV inactivate PGA through covalent inhibition. Continuous electron density connecting the inhibitor to both Thr20 and Tyr34 of the flexible loop was observed providing strong evidence that Thr20 is the primary catalytic nucleophile and that Tyr34 plays an important role in catalysis as well. The unexpected covalent binding observed in the PGA-DON and PGA-DONV complexes shows that a secondary reaction involving the formation of a Tyr34-inhibitor bond takes place with concomitant inactivation of PGA. The predicted covalent linkage is not seen, however, suggesting an alternative method of inhibition not yet seen for these diazo analogues. These surprising results give insight as to the role of the flexible loop Thr and Tyr in the catalytic mechanism. |
==About this Structure== | ==About this Structure== | ||
| - | 1DJO is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Pseudomonas_sp. Pseudomonas sp.] with CAB as [http://en.wikipedia.org/wiki/ligand ligand]. Active as [http://en.wikipedia.org/wiki/Glutamin-(asparagin-)ase Glutamin-(asparagin-)ase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.5.1.38 3.5.1.38] Full crystallographic information is available from [http:// | + | 1DJO is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Pseudomonas_sp. Pseudomonas sp.] with <scene name='pdbligand=CAB:'>CAB</scene> as [http://en.wikipedia.org/wiki/ligand ligand]. Active as [http://en.wikipedia.org/wiki/Glutamin-(asparagin-)ase Glutamin-(asparagin-)ase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.5.1.38 3.5.1.38] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1DJO OCA]. |
==Reference== | ==Reference== | ||
| Line 14: | Line 14: | ||
[[Category: Pseudomonas sp.]] | [[Category: Pseudomonas sp.]] | ||
[[Category: Single protein]] | [[Category: Single protein]] | ||
| - | [[Category: Lacount, M | + | [[Category: Lacount, M W.]] |
[[Category: Lebioda, L.]] | [[Category: Lebioda, L.]] | ||
[[Category: Lewinski, K.]] | [[Category: Lewinski, K.]] | ||
| Line 28: | Line 28: | ||
[[Category: suicide inhibitor]] | [[Category: suicide inhibitor]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 12:17:13 2008'' |
Revision as of 10:17, 21 February 2008
|
CRYSTAL STRUCTURE OF PSEUDOMONAS 7A GLUTAMINASE-ASPARAGINASE WITH THE INHIBITOR DONV COVALENTLY BOUND IN THE ACTIVE SITE
Overview
Pseudomonas 7A glutaminase-asparaginase (PGA) catalyzes the hydrolysis of D and L isomers of glutamine and asparagine. Crystals of PGA were reacted with diazo analogues of glutamine (6-diazo-5-oxo-L-norleucine, DON) and asparagine (5-diazo-4-oxo-L-norvaline, DONV), which are known inhibitors of the enzyme. The derivatized crystals remained isomorphous to native PGA crystals. Their structures were refined to crystallographic R = 0.20 and R(free) = 0.24 for PGA-DON and R = 0.19 and R = 0.23 for PGA-DONV. Difference Fourier electron density maps clearly showed that both DON and DONV inactivate PGA through covalent inhibition. Continuous electron density connecting the inhibitor to both Thr20 and Tyr34 of the flexible loop was observed providing strong evidence that Thr20 is the primary catalytic nucleophile and that Tyr34 plays an important role in catalysis as well. The unexpected covalent binding observed in the PGA-DON and PGA-DONV complexes shows that a secondary reaction involving the formation of a Tyr34-inhibitor bond takes place with concomitant inactivation of PGA. The predicted covalent linkage is not seen, however, suggesting an alternative method of inhibition not yet seen for these diazo analogues. These surprising results give insight as to the role of the flexible loop Thr and Tyr in the catalytic mechanism.
About this Structure
1DJO is a Single protein structure of sequence from Pseudomonas sp. with as ligand. Active as Glutamin-(asparagin-)ase, with EC number 3.5.1.38 Full crystallographic information is available from OCA.
Reference
Reactions of Pseudomonas 7A glutaminase-asparaginase with diazo analogues of glutamine and asparagine result in unexpected covalent inhibitions and suggests an unusual catalytic triad Thr-Tyr-Glu., Ortlund E, Lacount MW, Lewinski K, Lebioda L, Biochemistry. 2000 Feb 15;39(6):1199-204. PMID:10684596
Page seeded by OCA on Thu Feb 21 12:17:13 2008
