Native Carboxypeptidase A in a New Crystal Environment Reveals a Different Conformation of the Important Tyrosine 248

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• 作者：Jens Thostrup Bukrinsky ; Morten Jannik Bjerrum ; and Anders Kadziola
• 刊名：Biochemistry
• 出版年：1998
• 出版时间：November 24, 1998
• 年：1998
• 卷：37
• 期：47
• 页码：16555 - 16564
• 全文大小：264K
• 年卷期：v.37,no.47(November 24, 1998)
• ISSN：1520-4995

文摘

Native carboxypeptidase A has been crystallized in a new crystal form, and the structure hasbeen refined with X-ray data to 2.0 Å resolution. In contrast to the previously published structure [Rees,D. C., Lewis, M., and Lipscomb, W. N. (1983) J. Mol. Biol. 168, 367-387], no active-site amino acidsare involved in the crystal packing. The important Tyr248 is stabilized inside the active site by a hydrogenbond and by interactions with Ile247. The proposed role of Tyr248 in the induced fit mechanism istherefore not supported by the findings in this structure of native carboxypeptidase A. The structure hasa partly populated inhibitory Zn²⁺ site in close proximity to the catalytic Zn²⁺ as evident from X-rayanomalous dispersion data. A hydroxo bridge is found between the catalytic Zn²⁺ and the inhibitoryZn²⁺ with a Zn²⁺-Zn²⁺ distance of 3.48 Å. In addition, the inhibitory Zn²⁺ has Glu270 as a monodentateligand. No other protein ligands to the inhibitory Zn²⁺ are seen. The crystals were grown at 0.3 M LiCland weak evidence for a binding site for partly competitive inhibitory anions is observed.