1yf8: Difference between revisions

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[[Image:1yf8.gif|left|200px]]
{{Seed}}
[[Image:1yf8.png|left|200px]]


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{{STRUCTURE_1yf8|  PDB=1yf8  |  SCENE=  }}  
{{STRUCTURE_1yf8|  PDB=1yf8  |  SCENE=  }}  


'''Crystal structure of Himalayan mistletoe RIP reveals the presence of a natural inhibitor and a new functionally active sugar-binding site'''
===Crystal structure of Himalayan mistletoe RIP reveals the presence of a natural inhibitor and a new functionally active sugar-binding site===




==Overview==
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Ribosome-inactivating proteins (RIPs) are toxins involved in plant defense. How the plant prevents autotoxicity is not yet fully understood. The present study is the first structural evidence of a naturally inhibited form of RIP from a plant. Himalayan mistletoe RIP (HmRIP) was purified from Viscum album leaves and crystallized with lactose. The structure was determined by the molecular replacement method and refined at 2.8-A resolution. The crystal structure revealed the presence of high quality non-protein electron density at the active site, into which a pteridine derivative (2-amino 4-isopropyl 6-carboxyl pteridine) was modeled. The carboxyl group of the ligand binds strongly with the key active site residue Arg(162), nullifies the positive charge required for catalysis, and thereby acts as a natural inhibitor. Lectin subunits of RIPs have two active sugar-binding sites present in 1alpha- and 2gamma-subdomains. A third functionally active site has been identified in the 1beta-subdomain of HmRIP. The 1beta-site is active despite the absence of conserved polar sugar-binding residues. Loss of these residues is compensated by the following: (i) the presence of an extended site where the penultimate sugar also interacts with the protein; (ii) the interactions of galactose with the protein main chain carbonyl and amide nitrogen atoms; (iii) the presence of a well defined pocket encircled by four walls; and (iv) a favorable stacking of the galactose ring with Tyr(66) besides the conserved Phe(75). The mode of sugar binding is also distinct at the 1alpha and 2gamma sugar-binding sites.
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{{ABSTRACT_PUBMED_15774467}}


==About this Structure==
==About this Structure==
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[[Category: Sugar-binding site]]
[[Category: Sugar-binding site]]
[[Category: Viscum album]]
[[Category: Viscum album]]
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May  3 16:14:51 2008''
 
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jul 28 14:24:27 2008''

Revision as of 11:24, 28 July 2008

File:1yf8.png

Template:STRUCTURE 1yf8

Crystal structure of Himalayan mistletoe RIP reveals the presence of a natural inhibitor and a new functionally active sugar-binding site

Template:ABSTRACT PUBMED 15774467

About this Structure

1YF8 is a Protein complex structure of sequences from Viscum album. Full crystallographic information is available from OCA.

Reference

Crystal structure of himalayan mistletoe ribosome-inactivating protein reveals the presence of a natural inhibitor and a new functionally active sugar-binding site., Mishra V, Bilgrami S, Sharma RS, Kaur P, Yadav S, Krauspenhaar R, Betzel C, Voelter W, Babu CR, Singh TP, J Biol Chem. 2005 May 27;280(21):20712-21. Epub 2005 Mar 17. PMID:15774467

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