Factor IX: Difference between revisions

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Nadia Dorochko, Alexander Berchansky, David Canner, Michal Harel

Revision as of 07:46, 27 April 2009 view source Nadia Dorochko (talk \| contribs) 420 edits No edit summary ← Older edit		Revision as of 07:49, 27 April 2009 view source Nadia Dorochko (talk \| contribs) 420 edits No edit summary Newer edit →
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	The serine protease domain of FIX accounts for half of its mass and contains a conserved catalytic triad made of Asp, His, and Ser. The binding pockets of these vitamin-K depended proteases recognize a small number of amino acids sequences allowing them to cleave at arginyl residues with high substrate specificity. Serine’s hydroxyl group carries out the nucleophillic attack. While the imidazol ring of hisidine takes up the liberated proton and the carboxylate ion of Asp stabilizes the developing charge. Unlike other serine protease family members these vitamin K dependent proteases have an extended specificity pocket which allows a small number of amino acids to be recognized.		The serine protease domain of FIX accounts for half of its mass and contains a conserved catalytic triad made of Asp, His, and Ser. The binding pockets of these vitamin-K depended proteases recognize a small number of amino acids sequences allowing them to cleave at arginyl residues with high substrate specificity. Serine’s hydroxyl group carries out the nucleophillic attack. While the imidazol ring of hisidine takes up the liberated proton and the carboxylate ion of Asp stabilizes the developing charge. Unlike other serine protease family members these vitamin K dependent proteases have an extended specificity pocket which allows a small number of amino acids to be recognized.

	The catalytic domain of FIX is composed of two β-<scene name='Factor_IX/Rfnscene/3'>barrel</scene> subdomains that form an active site at their interface. The active site is located at the junction of these β-barrels. The EGF-2 domain is connected to the catalytic domain through a disulfide bridge and is opposite to the active site. There are three disulfide bonds, and the C-terminus contains helical structures that run across the N-terminus of the β-barrel. The catalytic domain contains a calcium binding site that exposes the 148-loop for proteolytic cleavage. This calcium ion is stabilized by Glu-70, Glu-77, Glu-80 and a main chain oxygens of Asn-72 and Glu-75. This site seems to be preformed, unlike the calcium binding sites that are generated in the Gla domain upon calcium binding.		The catalytic domain of FIX is composed of two β-<scene name='Factor_IX/Rfnscene/3'>barrel</scene> subdomains that form an active site at their interface. The active site is located at the junction of these β-barrels. The EGF-2 domain is connected to the catalytic domain through a disulfide bridge and is opposite to the active site. There are three disulfide bonds, and the C-terminus contains helical structures that run across the N-terminus of the β-barrel. The catalytic domain contains a calcium binding site that exposes the <scene name='Factor_IX/Rfnscene_4/1'>148-loop</scene> for proteolytic cleavage. This calcium ion is stabilized by Glu-70, Glu-77, Glu-80 and a main chain oxygens of Asn-72 and Glu-75. This site seems to be preformed, unlike the calcium binding sites that are generated in the Gla domain upon calcium binding.