Carp muscle calcium-binding protein. II. Structure determination and general description.
Carp muscle calcium-binding protein. II. Structure determination and general description.
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DOI：
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发表时间：
1973-05
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影响因子：
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通讯作者：
R. Kretsinger;C. Nockolds
中科院分区：
文献类型：
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作者：
R. Kretsinger;C. Nockolds
摘要用X射线衍射法测定了鲤鱼肌肉钙结合蛋白(小蛋白)的结构，其分辨率为1.85A。用进动照相法测量了3-氯汞-2-甲氧基丙基脲、溴化汞和乙基氯化汞三种重原子衍生物在2.0-A分辨率下的同象和反常散射数据。如文件III所述，在本系列中，2.0-A相被细化，而2.0-到1.85-A相通过使用切线公式来确定。电子密度图根据本系列论文I中描述的108个氨基酸序列进行解释。一个钙离子结合在螺旋C和螺旋D之间的环中，第二个钙离子结合在EF环中。整个CD区域与螺旋E、EF环和末端螺旋F通过大约分子内2倍轴相关。虽然AB区不结合钙，但它的结构类似于CD和EF区，似乎是基因三倍复制的结果。该分子通常是球形的，有一个定义良好的疏水核心，占其总体积的七分之一，由苯丙氨酸、异亮氨酸、亮氨酸和缬氨酸的侧链组成。除了与钙结合和精氨酸-75和谷氨酸-81之间具有不变的内部盐桥的那些外，所有的极性侧链都在表面。
Abstract The structure of crystalline carp muscle calcium-binding protein (parvalbumin) has been determined by x-ray diffraction techniques to nominal 1.85-A resolution. Isomorphous and anomalous scattering data were measured for three heavy atom derivatives, 3-chloromercuri-2-methoxypropyl urea, mercury bromide, and ethyl mercury chloride, to 2.0-A resolution using precession photography. As described in Paper III in this series the 2.0-A phases were refined and the 2.0- to 1.85-A phases were determined by use of the tangent formula. The electron density map is interpreted in terms of the 108 amino acid sequence described in Paper I in this series. A calcium ion is bound in the loop between helix C and helix D and a second calcium is bound in the EF loop. The entire CD region is related to helix E, the EF loop, and the terminal helix F by an approximate intramolecular 2-fold axis. Although it does not bind calcium the AB region has a structure similar to the CD and EF regions and appears to have resulted from a gene triplication. The molecule is generally spherical with a well defined hydrophobic core, one-seventh of its total volume, composed of side chains of phenylalanine, isoleucine, leucine, and valine. All of the polar side chains are at the surface except those associated with calcium binding and with an invariant internal salt bridge between arginine-75 and glutamic acid-81.