期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1971
卷号：68
期号：8
页码：1853-1857
DOI：10.1073/pnas.68.8.1853
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Concanavalin A, a phytohemagglutinin isolated from the jack bean, crystallizes at pH 6.8 in the orthorhombic space group 1222 with a = 89.9, b = 87.2, and c = 63.1 A. We have analyzed x-ray diffraction intensity data to 4 A resolution on native concanavalin A and five heavy-metal derivatives: lead, mersalyl, chloroplatinate, uranyl, and o-mercuri-p-nitrophenol. Heavy-atom positions, occupancies, and isotropic thermal parameters have been refined by least-squares methods. The electron density maps clearly show the molecular shape and the packing of the concanavalin A molecules. The asymmetric unit (mol wt 27,000) forms an elliptical dome or "gumdrop" with a base of approximately 46 x 26 A and a height of 42 A. The subunits are paired across 2-fold axes parallel to the c-axis to form dimers. The dimers are in turn paired across points of D2 symmetry to form tetramers of roughly tetrahedral shape. Each unit has a depression located on the surface which could be the site of saccharide binding. In many regions we have been able to trace the course of the polypeptide chain.
