1ift
From Proteopedia
| Line 4: | Line 4: | ||
==Overview== | ==Overview== | ||
| - | Ricin is a potent plant toxin which acts by removing a specific adenine | + | Ricin is a potent plant toxin which acts by removing a specific adenine residue from the ribosome. The X-ray crystal structure of a new, tetragonal crystal form of the recombinant ricin A-chain diffracting to 1.8 A resolution has been determined via molecular replacement methods and refined to a crystallographic R-factor of 18.6%. The higher resolution electron density allowed improvements to be made upon previously published models, resulting in an increase in the assigned secondary structure of the protein. The enzyme adopts the same global conformation in this crystal form with differences in detail due only partly to crystal packing. The active site superimposes closely with those of previously published models but the locations of the active-site water molecules differ in this structure. To address the current mechanistic model, an additional two structures are presented: recombinant ricin A-chain complexed with the substrate analogue formycin monophosphate as well as with adenosine monophosphate, which is cleaved by the crystalline enzyme. The formycin monophosphate displaces a putative catalytic water molecule. This supports the notion that the analogue does not bind in a transition state conformation and that contacts from other elements of the 28 S RNA natural substrate are required to achieve full reactivity. The structure of the adenosine monophosphate complex suggests a mechanism for the release of the adenine product via of the side-chain Tyr80. The structures suggest that Glu177 is better positioned for the activation of the catalytic water molecule than Arg180. |
==About this Structure== | ==About this Structure== | ||
| Line 14: | Line 14: | ||
[[Category: Single protein]] | [[Category: Single protein]] | ||
[[Category: rRNA N-glycosylase]] | [[Category: rRNA N-glycosylase]] | ||
| - | [[Category: Derbyshire, D | + | [[Category: Derbyshire, D J.]] |
| - | [[Category: Pauptit, R | + | [[Category: Pauptit, R A.]] |
| - | [[Category: Thatcher, D | + | [[Category: Thatcher, D R.]] |
| - | [[Category: Tucker, A | + | [[Category: Tucker, A D.]] |
| - | [[Category: Weston, S | + | [[Category: Weston, S A.]] |
[[Category: glycoprotein]] | [[Category: glycoprotein]] | ||
[[Category: glycosidase]] | [[Category: glycosidase]] | ||
| Line 24: | Line 24: | ||
[[Category: toxin]] | [[Category: toxin]] | ||
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 13:11:25 2008'' |
Revision as of 11:11, 21 February 2008
|
RICIN A-CHAIN (RECOMBINANT)
Overview
Ricin is a potent plant toxin which acts by removing a specific adenine residue from the ribosome. The X-ray crystal structure of a new, tetragonal crystal form of the recombinant ricin A-chain diffracting to 1.8 A resolution has been determined via molecular replacement methods and refined to a crystallographic R-factor of 18.6%. The higher resolution electron density allowed improvements to be made upon previously published models, resulting in an increase in the assigned secondary structure of the protein. The enzyme adopts the same global conformation in this crystal form with differences in detail due only partly to crystal packing. The active site superimposes closely with those of previously published models but the locations of the active-site water molecules differ in this structure. To address the current mechanistic model, an additional two structures are presented: recombinant ricin A-chain complexed with the substrate analogue formycin monophosphate as well as with adenosine monophosphate, which is cleaved by the crystalline enzyme. The formycin monophosphate displaces a putative catalytic water molecule. This supports the notion that the analogue does not bind in a transition state conformation and that contacts from other elements of the 28 S RNA natural substrate are required to achieve full reactivity. The structure of the adenosine monophosphate complex suggests a mechanism for the release of the adenine product via of the side-chain Tyr80. The structures suggest that Glu177 is better positioned for the activation of the catalytic water molecule than Arg180.
About this Structure
1IFT is a Single protein structure of sequence from Ricinus communis. Active as rRNA N-glycosylase, with EC number 3.2.2.22 Known structural/functional Site: . Full crystallographic information is available from OCA.
Reference
X-ray structure of recombinant ricin A-chain at 1.8 A resolution., Weston SA, Tucker AD, Thatcher DR, Derbyshire DJ, Pauptit RA, J Mol Biol. 1994 Dec 9;244(4):410-22. PMID:7990130
Page seeded by OCA on Thu Feb 21 13:11:25 2008
