1i9h: Difference between revisions
No edit summary |
No edit summary |
||
| Line 1: | Line 1: | ||
[[Image:1i9h.gif|left|200px]] | [[Image:1i9h.gif|left|200px]] | ||
<!-- | |||
The line below this paragraph, containing "STRUCTURE_1i9h", creates the "Structure Box" on the page. | |||
You may change the PDB parameter (which sets the PDB file loaded into the applet) | |||
or the SCENE parameter (which sets the initial scene displayed when the page is loaded), | |||
or leave the SCENE parameter empty for the default display. | |||
--> | |||
{{STRUCTURE_1i9h| PDB=1i9h | SCENE= }} | |||
}} | |||
'''CORE STREPTAVIDIN-BNA COMPLEX''' | '''CORE STREPTAVIDIN-BNA COMPLEX''' | ||
| Line 30: | Line 27: | ||
[[Category: Livnah, O.]] | [[Category: Livnah, O.]] | ||
[[Category: Wilchek, M.]] | [[Category: Wilchek, M.]] | ||
[[Category: | [[Category: Classical beta barrel]] | ||
[[Category: | [[Category: Protein-ligand complex]] | ||
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 19:44:20 2008'' | |||
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on | |||
Revision as of 19:44, 2 May 2008
CORE STREPTAVIDIN-BNA COMPLEX
OverviewOverview
Avidin and its bacterial analogue streptavidin exhibit similarly high affinities toward the vitamin biotin. The extremely high affinity of these two proteins has been utilized as a powerful tool in many biotechnological applications. Although avidin and streptavidin have similar tertiary and quaternary structures, they differ in many of their properties. Here we show that avidin enhances the alkaline hydrolysis of biotinyl p-nitrophenyl ester, whereas streptavidin protects this reaction even under extreme alkaline conditions (pH > 12). Unlike normal enzymatic catalysis, the hydrolysis reaction proceeds as a single cycle with no turnover because of the extremely high affinity of the protein for one of the reaction products (i.e. free biotin). The three-dimensional crystal structures of avidin (2 A) and streptavidin (2.4 A) complexed with the amide analogue, biotinyl p-nitroanilide, as a model for the p-nitrophenyl ester, revealed structural insights into the factors that enhance or protect the hydrolysis reaction. The data demonstrate that several molecular features of avidin are responsible for the enhanced hydrolysis of biotinyl p-nitrophenyl ester. These include the nature of a decisive flexible loop, the presence of an obtrusive arginine 114, and a newly formed critical interaction between lysine 111 and the nitro group of the substrate. The open conformation of the loop serves to expose the substrate to the solvent, and the arginine shifts the p-nitroanilide moiety toward the interacting lysine, which increases the electron withdrawing characteristics and consequent electrophilicity of the carbonyl group of the substrate. Streptavidin lacked such molecular properties, and analogous interactions with the substrate were consequently absent. The information derived from these structures may provide insight into the action of artificial protein catalysts and the evolution of catalytic sites in general.
About this StructureAbout this Structure
1I9H is a Single protein structure of sequence from Streptomyces avidinii. Full crystallographic information is available from OCA.
ReferenceReference
Chicken avidin exhibits pseudo-catalytic properties. Biochemical, structural, and electrostatic consequences., Huberman T, Eisenberg-Domovich Y, Gitlin G, Kulik T, Bayer EA, Wilchek M, Livnah O, J Biol Chem. 2001 Aug 24;276(34):32031-9. Epub 2001 Jun 6. PMID:11395489 Page seeded by OCA on Fri May 2 19:44:20 2008