Fingeroth J D
Laboratory of Infectious Diseases, Dana-Farber Cancer Institute, Boston, MA 02115.
J Immunol. 1990 May 1;144(9):3458-67.
The complete nucleotide sequence of murine complement receptor type 2 (CR2) was determined from two overlapping cDNA clones derived from a lambda gt11 library of late pre-B cell origin. Comparison of the predicted sequence of the 1014 amino acid murine homolog with that of human CR2 revealed marked evolutionary conservation. The murine molecule was 65% identical to human CR2 overall, lacking a single repetitive sequence variably present in man. The 15 approximately 60-75 amino acid short consensus repeats (SCR) that constitute the entire extracellular domain of murine CR2 were 53 to 81% identical to and could be directly aligned with the human protein. As reported, the cytoplasmic tail shared 79% amino acid identity with human CR2, whereas that of the transmembrane was only 33%. Murine CR2 contained 16 potential N-linked glycosylation sites of which 6 were conserved, 4 altered, and 6 lost during human evolution. The hydropathicity profile of the two molecules was nearly colinear with some variation in the N-terminal region of the first repeat, as well as within the sixth and twelfth repeats. RNA blot analysis revealed a approximately 4.0 to 5.0 kb message in murine B lymphocytes, which was absent in T lymphocytes (thymus and spleen), liver, brain, lung, kidney, and heart. A method was devised to more precisely compare the repeat structures. An identity matrix analysis suggests that human ancestral CR2 evolved before divergence of the rodent and primate branches of the evolutionary tree through a series of predictable gene duplications, possibly giving rise to the precursor of human CR1 and murine CRY. The marked structural similarity between the human and murine receptors suggests functional conservation as well.
从小鼠晚期前B细胞来源的λgt11文库中获得的两个重叠cDNA克隆，测定了小鼠2型补体受体（CR2）的完整核苷酸序列。将预测的1014个氨基酸的小鼠同源物序列与人CR2序列进行比较，发现有明显的进化保守性。小鼠分子与人CR2总体上有65%的同一性，缺少人类中可变存在的单个重复序列。构成小鼠CR2整个细胞外结构域的15个约60 - 75个氨基酸的短共有重复序列（SCR）与人蛋白质的同一性为53%至81%，并且可以直接比对。如所报道的，胞质尾与人CR2的氨基酸同一性为79%，而跨膜区仅为33%。小鼠CR2含有16个潜在的N - 连接糖基化位点，其中6个是保守的，4个发生了改变，并在人类进化过程中丢失了6个。这两种分子的亲水性图谱几乎是共线的，只是在第一个重复序列的N端区域以及第六和第十二个重复序列内有一些变化。RNA印迹分析显示在小鼠B淋巴细胞中有一条约4.0至5.0 kb的条带，而在T淋巴细胞（胸腺和脾脏）、肝脏、大脑、肺、肾脏和心脏中则没有。设计了一种方法来更精确地比较重复结构。同一性矩阵分析表明，人类祖先的CR2在进化树的啮齿动物和灵长类分支分化之前，通过一系列可预测的基因复制而进化，可能产生了人类CR1和小鼠CRY的前体。人类和小鼠受体之间明显的结构相似性也表明了功能上的保守性。
