Structure of Chymopapain at 1.7 Å Resolution

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• 作者：Dominique Maes ; Julie Bouckaert ; Freddy Poortmans ; Lode Wyns ; and Yvan Looze
• 刊名：Biochemistry
• 出版年：1996
• 出版时间：December 17, 1996
• 年：1996
• 卷：35
• 期：50
• 页码：16292 - 16298
• 全文大小：336K
• 年卷期：v.35,no.50(December 17, 1996)
• ISSN：1520-4995

文摘

The X-ray structure of chymopapain, a cysteine proteinase isolatedfrom the latex of the fruitsof Carica papaya L., has been determined by molecularreplacement methods and refined to a conventionalR factor of 0.19 for all observed reflections in the rangefrom 9.5 to 1.7 Å resolution. The crystals usedin this study contained a unique molecular species of chymopapain withtwo moles of thiomethyl attachedto the two free cysteines per mole of enzyme. A comparison is madewith the other known papayaproteinase X-ray structures: papain, caricain, and glycylendopeptidase. Their backbone conformationsare extremely similar except for two loop regions. Both regionsare located at the surface of the proteinand far away of the active site cleft. In each X-ray structure thesame water network was found at theinterface between the two domains of the enzyme. A closeexamination of the active site groove showedthat the specificity restrictions dictated by the S2 subsite did notdiffer significantly among the fourproteinases.