Lin P, Le-Niculescu H, Hofmeister R, McCaffery J M, Jin M, Hennemann H, McQuistan T, De Vries L, Farquhar M G
Division of Cellular and Molecular Medicine and Department of Pathology, University of California, San Diego, La Jolla, California 92093-0651, USA.
J Cell Biol. 1998 Jun 29;141(7):1515-27. doi: 10.1083/jcb.141.7.1515.
We have identified CALNUC, an EF-hand, Ca2+-binding protein, as a Golgi resident protein. CALNUC corresponds to a previously identified EF-hand/calcium-binding protein known as nucleobindin. CALNUC interacts with Galphai3 subunits in the yeast two-hybrid system and in GST-CALNUC pull-down assays. Analysis of deletion mutants demonstrated that the EF-hand and intervening acidic regions are the site of CALNUC's interaction with Galphai3. CALNUC is found in both cytosolic and membrane fractions. The membrane pool is tightly associated with the luminal surface of Golgi membranes. CALNUC is widely expressed, as it is detected by immunofluorescence in the Golgi region of all tissues and cell lines examined. By immunoelectron microscopy, CALNUC is localized to cis-Golgi cisternae and the cis-Golgi network (CGN). CALNUC is the major Ca2+-binding protein detected by 45Ca2+-binding assay on Golgi fractions. The properties of CALNUC and its high homology to calreticulin suggest that it may play a key role in calcium homeostasis in the CGN and cis-Golgi cisternae.
我们已确定CALNUC（一种EF手型钙结合蛋白）为高尔基体驻留蛋白。CALNUC与先前鉴定的一种名为核结合蛋白的EF手型/钙结合蛋白相对应。在酵母双杂交系统和GST - CALNUC下拉实验中，CALNUC与Galphai3亚基相互作用。对缺失突变体的分析表明，EF手型结构域和中间的酸性区域是CALNUC与Galphai3相互作用的位点。CALNUC存在于胞质和膜组分中。膜池与高尔基体膜的腔表面紧密相连。CALNUC广泛表达，在所检测的所有组织和细胞系的高尔基体区域通过免疫荧光均可检测到。通过免疫电子显微镜观察，CALNUC定位于顺式高尔基体潴泡和顺式高尔基体网络（CGN）。CALNUC是在高尔基体组分上通过45Ca2+结合实验检测到的主要钙结合蛋白。CALNUC的特性及其与钙网蛋白的高度同源性表明，它可能在CGN和顺式高尔基体潴泡的钙稳态中起关键作用。
