Structure of Ca(2+)-loaded human grancalcin.
Structure of Ca(2+)-loaded human grancalcin.
复制标题
负载 Ca(2) 的人大钙蛋白的结构。
DOI：
10.1107/s0907444901016511
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发表时间：
2001
期刊：
影响因子：
--
通讯作者：
M. Cygler
中科院分区：
文献类型：
--
作者：
J. Jia;N. Borregaard;K. Lollike;M. Cygler
Grancalcin是一种细胞质Ca（2+）结合蛋白，最初在人中性粒细胞中发现。它属于一类新的EF-hand蛋白，称为PEF蛋白，它包含五个EF-hand基序。在粗钙素的n端有大约50个富含甘氨酸和脯氨酸的残基长片段。单体内未配对的第五个EF-hand通过与第二个分子中的对应物配对提供了二聚化的手段。全长巨钙素为载脂蛋白形式，二聚体中有一个EF3被Ca（2+）离子占据。虽然分子中存在n端片段，但这部分在晶体中是无序的。本文给出了在Ca（2+）存在和不存在的情况下，缺乏52个n端残基的截断形式的grancalcin的结构。在Ca（2+）结合形式中，离子存在于EF1和EF3手上。Ca（2+）与这两个EF手结合只产生很小的构象变化，主要发生在EF1 Ca（2+）结合环内。这一观察结果支持了基于同源蛋白ALG-2结构的假设，该结构显示EF4和EF5与grancalcin在取向上存在显著差异，即钙是诱发PEF蛋白显著构象变化的必要因素，但不是单独的充分因素。
Grancalcin is a cytosolic Ca(2+)-binding protein originally identified in human neutrophils. It belongs to a new class of EF-hand proteins, called PEF proteins, which contain five EF-hand motifs. At the N-terminus of grancalcin there is a approximately 50 residue-long segment rich in glycines and prolines. The fifth EF-hand, unpaired within the monomer, provides a means for dimerization through pairing with its counterpart in a second molecule. The structure of full-length grancalcin in the apo form and with one EF3 within the dimer occupied by a Ca(2+) ion have been determined. Although the N-terminal segment was present in the molecule, this part was disordered in the crystals. Here, the structure of a truncated form of grancalcin, which is lacking 52 N-terminal residues, in the presence and absence of Ca(2+) is presented. In the Ca(2+)-bound form the ions are found in the EF1 and EF3 hands. Binding of Ca(2+) to these two EF hands produces only minor conformational changes, mostly within the EF1 Ca(2+)-binding loop. This observation supports the hypothesis, formulated on the basis of the structure of a homologous protein ALG-2 which shows significant differences in the orientation of EF4 and EF5 compared with grancalcin, that calcium is a necessary factor but not sufficient alone for inducing a significant conformational change in PEF proteins.