Weng X, Luecke H, Song I S, Kang D S, Kim S H, Huber R
Department of Molecular and Cell Biology, University of California, Berkeley 94720.
Protein Sci. 1993 Mar;2(3):448-58. doi: 10.1002/pro.5560020317.
cDNA coding for N-terminally truncated human annexin I, a member of the family of Ca(2+)-dependent phospholipid binding proteins, has been cloned and expressed in Escherichia coli. The expressed protein is biologically active, and has been purified and crystallized in space group P2(1)2(1)2(1) with cell dimensions a = 139.36 A, b = 67.50 A, and c = 42.11 A. The crystal structure has been determined by molecular replacement at 3.0 A resolution using the annexin V core structure as the search model. The average backbone deviation between these two structures is 2.34 A. The structure has been refined to an R-factor of 17.7% at 2.5 A resolution. Six calcium sites have been identified in the annexin I structure. Each is located in the loop region of the helix-loop-helix motif. Two of the six calcium sites in annexin I are not occupied in the annexin V structure. The superpositions of the corresponding loop regions in the four domains show that the calcium binding loops in annexin I can be divided into two classes: type II and type III. Both classes are different from the well-known EF-hand motif (type I).
编码N端截短的人膜联蛋白I（一种Ca(2+)依赖性磷脂结合蛋白家族成员）的cDNA已被克隆并在大肠杆菌中表达。所表达的蛋白具有生物活性，并且已在空间群P2(1)2(1)2(1)中纯化并结晶，晶胞参数为a = 139.36 Å，b = 67.50 Å，c = 42.11 Å。晶体结构已通过分子置换法在3.0 Å分辨率下确定，使用膜联蛋白V核心结构作为搜索模型。这两种结构之间的平均主链偏差为2.34 Å。该结构已在2.5 Å分辨率下精修至R因子为17.7%。在膜联蛋白I结构中已鉴定出六个钙结合位点。每个位点都位于螺旋-环-螺旋基序的环区域。膜联蛋白I的六个钙结合位点中有两个在膜联蛋白V结构中未被占据。四个结构域中相应环区域的叠加显示，膜联蛋白I中的钙结合环可分为两类：II型和III型。这两类都与著名的EF手基序（I型）不同。
