View source for 1b7x

[[Image:1b7x.jpg|left|200px]]

 {{Structure
|PDB= 1b7x |SIZE=350|CAPTION= <scene name='initialview01'>1b7x</scene>, resolution 2.10&Aring;
|SITE= 
|LIGAND= 
|ACTIVITY= <span class='plainlinks'>[http://en.wikipedia.org/wiki/Thrombin Thrombin], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.4.21.5 3.4.21.5] </span>
|GENE= 
|DOMAIN=
|RELATEDENTRY=
|RESOURCES=<span class='plainlinks'>[http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=1b7x FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1b7x OCA], [http://www.ebi.ac.uk/pdbsum/1b7x PDBsum], [http://www.rcsb.org/pdb/explore.do?structureId=1b7x RCSB]</span>
}}

'''STRUCTURE OF HUMAN ALPHA-THROMBIN Y225I MUTANT BOUND TO D-PHE-PRO-ARG-CHLOROMETHYLKETONE'''


==Overview==
Residue 225 in serine proteases of the chymotrypsin family is Pro or Tyr in more than 95% of nearly 300 available sequences. Proteases with Y225 (like some blood coagulation and complement factors) are almost exclusively found in vertebrates, whereas proteases with P225 (like degradative enzymes) are present from bacteria to human. Saturation mutagenesis of Y225 in thrombin shows that residue 225 affects ligand recognition up to 60,000-fold. With the exception of Tyr and Phe, all residues are associated with comparable or greatly reduced catalytic activity relative to Pro. The crystal structures of three mutants that differ widely in catalytic activity (Y225F, Y225P, and Y225I) show that although residue 225 makes no contact with substrate, it drastically influences the shape of the water channel around the primary specificity site. The activity profiles obtained for thrombin also suggest that the conversion of Pro to Tyr or Phe documented in the vertebrates occurred through Ser and was driven by a significant gain (up to 50-fold) in catalytic activity. In fact, Ser and Phe are documented in 4% of serine proteases, which together with Pro and Tyr account for almost the entire distribution of residues at position 225. The unexpected crucial role of residue 225 in serine proteases explains the evolutionary selection of residues at this position and shows that the structural determinants of protease activity and specificity are more complex than currently believed. These findings have broad implications in the rational design of enzymes with enhanced catalytic properties.

==About this Structure==
1B7X is a [[Protein complex]] structure of sequences from [http://en.wikipedia.org/wiki/Homo_sapiens Homo sapiens]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1B7X OCA]. 

==Reference==
Unexpected crucial role of residue 225 in serine proteases., Guinto ER, Caccia S, Rose T, Futterer K, Waksman G, Di Cera E, Proc Natl Acad Sci U S A. 1999 Mar 2;96(5):1852-7. PMID:[http://www.ncbi.nlm.nih.gov/pubmed/10051558 10051558]
[[Category: Homo sapiens]]
[[Category: Protein complex]]
[[Category: Thrombin]]
[[Category: Caccia, S.]]
[[Category: Cera, E Di.]]
[[Category: Futterer, K.]]
[[Category: Waksman, G.]]
[[Category: serine protease]]

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