View source for 1k21

[[Image:1k21.jpg|left|200px]]<br /><applet load="1k21" size="350" color="white" frame="true" align="right" spinBox="true" 
caption="1k21, resolution 1.86&Aring;" />
'''HUMAN THROMBIN-INHIBITOR COMPLEX'''<br />

==Overview==
The binding of a series of low molecular weight ligands towards trypsin and thrombin has been studied by isothermal titration calorimetry and protein crystallography. In a series of congeneric ligands, surprising changes of protonation states occur and are overlaid on the binding process. They result from induced pK(a) shifts depending on the local environment experienced by the ligand and protein functional groups in the complex (induced dielectric fit). They involve additional heat effects that must be corrected before any conclusion on the binding enthalpy (DeltaH) and entropy (DeltaS) can be drawn. After correction, trends in both contributions can be interpreted in structural terms with respect to the hydrogen bond inventory or residual ligand motions. For all inhibitors studied, a strong negative heat capacity change (DeltaC(p)) is detected, thus binding becomes more exothermic and entropically less favourable with increasing temperature. Due to a mutual compensation, Gibbs free energy remains virtually unchanged. The strong negative DeltaC(p) value cannot solely be explained by the removal of hydrophobic surface portions of the protein or ligand from water exposure. Additional contributions must be considered, presumably arising from modulations of the local water structure, changes in vibrational modes or other ordering parameters. For thrombin, smaller negative DeltaC(p) values are observed for ligand binding in the presence of sodium ions compared to the other alkali ions, probably due to stabilising effects on the protein or changes in the bound water structure.

==Disease==
Known diseases associated with this structure: Dysprothrombinemia OMIM:[[http://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=176930 176930]], Hyperprothrombinemia OMIM:[[http://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=176930 176930]], Hypoprothrombinemia OMIM:[[http://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=176930 176930]]

==About this Structure==
1K21 is a [http://en.wikipedia.org/wiki/Protein_complex Protein complex] structure of sequences from [http://en.wikipedia.org/wiki/Hirudo_medicinalis Hirudo medicinalis] and [http://en.wikipedia.org/wiki/Homo_sapiens Homo sapiens] with <scene name='pdbligand=NA:'>NA</scene> and <scene name='pdbligand=IGN:'>IGN</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [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] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1K21 OCA]. 

==Reference==
Factorising ligand affinity: a combined thermodynamic and crystallographic study of trypsin and thrombin inhibition., Dullweber F, Stubbs MT, Musil D, Sturzebecher J, Klebe G, J Mol Biol. 2001 Oct 26;313(3):593-614. PMID:[http://ispc.weizmann.ac.il//pmbin/getpm?pmid=11676542 11676542]
[[Category: Hirudo medicinalis]]
[[Category: Homo sapiens]]
[[Category: Protein complex]]
[[Category: Thrombin]]
[[Category: Musil, D.]]
[[Category: Stubbs, M T.]]
[[Category: IGN]]
[[Category: NA]]
[[Category: complex (serine protease/inhibitor)]]

''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 13:29:12 2008''