Crystal structure of the thrombin mutant D221A/D222K: the Asp222:Arg187 ion-pair stabilizes the fast form

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• 作者：Pineda ; Agustin O. ; Zhang ; Erli ; Guinto ; Enriqueta R. ; Savvides ; Savvas N. ; Tulinsky ; Alexander ; et. al.
• 关键词：Thrombin ; Allostery ; Na⁺ binding ; Serine protease structure
• 刊名：Biophysical Chemistry
• 出版年：2004
• 出版时间：December 20, 2004
• 年：2004
• 卷：112
• 期：2-3
• 页码：253-256
• 全文大小：201 K

文摘

The thrombin mutant D221A/D222K (ARK) does not bind Na⁺ and has interesting functional properties intermediate between those of the slow and fast forms of wild type. We solved the X-ray crystal structure of ARK bound at exosite I with a fragment of hirudin at 2.4-?? resolution. The structure shows a slight collapse of the 186 and 220 loops into the Na⁺ binding site due to disruption of the Asp222:Arg187 ion-pair. The backbone O atoms of Arg221a and Lys224 are shifted into conformations that eliminate optimal interaction with Na⁺. A paucity of solvent molecules in the Na⁺ binding site is also noted, by analogy to what is seen in the structure of the slow form. These findings reinforce the crucial role of the Asp222:Arg187 ion-pair in stabilizing the fast form of thrombin.