STRUCTURAL STUDIES OF CANCER-RELATED PROTEINS

该子项目是利用NIH/NCRR资助的中心赠款提供的资源的许多研究子项目之一。子项目和研究者（PI）可能从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。所列机构为中心，不一定是研究者所在机构。两种钙依赖性半胱氨酸蛋白酶，<$-和<$-钙蛋白酶，参与各种钙相关的信号通路，但在其激活的钙需求方面有显着差异。使用在CHESS收集的衍射数据，我们已经确定了一个<$-like钙蛋白酶的结构，它具有85%<$-calpain序列（大亚基的前48个和后62个残基是来自m-钙蛋白酶的残基）和低钙需求。使用这种结构是因为钙蛋白酶本身表达太差。正如预期的那样，类钙蛋白酶的结构在整体折叠上与m-钙蛋白酶非常相似，但在两个方面有显著差异。与m-钙蛋白酶相比，在不存在Ca 2+的情况下，类钙蛋白酶中的催化三联体残基His和Cys更接近;并且Ca 2+结合EF-手基序的显著部分是无序的并且更灵活。这些结构上的差异意味着无Ca 2+的<$-钙蛋白酶可能代表了一种部分激活的结构，需要较低的Ca 2+浓度来触发其激活

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The two Ca2+-dependent cysteine proteases, ¿- and ¿-calpain, are involved in various Ca2+-linked signal pathways, but differ markedly in their Ca2+ requirements for activation. Using diffraction data collected at CHESS, we have determined the structure of a ¿-like calpain, which has 85% ¿-calpain sequence (the first 48 and the last 62 residues of the large subunit are those from m-calpain) and a low Ca2+ requirement. This construct was used because ¿-calpain itself is too poorly expressed. The structure of ¿-like calpain is very similar in overall fold to that of m-calpain as expected, but differs significantly in two aspects. In comparison with m-calpain, the catalytic triad residues in ¿-like calpain, His and Cys, are much closer together in the absence of Ca2+; and significant portions of the Ca2+-binding EF-hand motifs are disordered and more flexible. These structural differences imply that Ca2+-free ¿-calpain may represent a partially activated structure, requiring lower Ca2+ concentration to trigger its activation