MULTIPLE MURINE ALPHA-1-PROTEASE INHIBITOR GENES SHOW UNUSUAL EVOLUTIONARY DIVERGENCE
MULTIPLE MURINE ALPHA-1-PROTEASE INHIBITOR GENES SHOW UNUSUAL EVOLUTIONARY DIVERGENCE
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DOI：
10.1073/pnas.88.21.9417
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发表时间：
1991-11-01
影响因子：
11.1
通讯作者：
KRAUTER, KS
中科院分区：
文献类型：
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作者：
BORRIELLO, F;KRAUTER, KS
鼠 α-1-蛋白酶抑制剂 (α-1-PI) 由 12 号染色体上的一个小基因家族编码。对 α-1-PI 和其他丝氨酸蛋白酶抑制剂基因的研究表明，抑制剂反应中心的突变率异常高。使用 PCR 技术的改进，我们之前已经鉴定了 C57BL/6 小鼠基因组中存在的五个不同的 alpha-1-PI 反应位点序列。在本报告中，我们使用 cDNA 克隆技术来证明所有五个基因均在成年小鼠肝脏中表达。 DNA 序列分析显示，所表达的 5 个 mRNA 中的 3 个具有蛋氨酸 353 的取代，这对于同源人类蛋白 α-1-抗胰蛋白酶 (α-1-AT) 的正常活性至关重要。五个 cDNA 的 DNA 序列的比较表明，该蛋白质的羧基末端一半具有较高程度的多态性，并且在反应位点周围的狭窄区域中核苷酸变化的替换/沉默比率异常高。反应位点附近的多态性聚集与高替换/沉默比率相结合表明了一种显然选择α-1-PI基因功能多样性的进化机制。最后，将 α-1-PI 多态性残基的三维位置建模为 α-1-PI 超基因家族成员卵清蛋白晶体结构的同源位置，预测许多这些氨基酸位于表面，可能与蛋白酶靶标相互作用。
The murine alpha-1-protease inhibitors (alpha-1-PI) are encoded by a small gene family on chromosome 12. Studies of alpha-1-PI and other serine protease inhibitor genes have revealed an unusually high rate of mutation of the reactive centers of the inhibitors. Using a modification of the PCR technique, we have previously identified rive distinct alpha-1-PI reactive site sequences present in the genome of C57BL/6 mice. In this report, we use cDNA cloning techniques to demonstrate that all five genes are expressed in the adult mouse liver. DNA sequence analysis shows that three of the five mRNAs expressed have a substitution for methionine-353, which is essential for normal activity of the homologous human protein, alpha-1-antitrypsin (alpha-1-AT). Comparison of the DNA sequences of the five cDNAs indicates a higher degree of polymorphism in the carboxyl-terminal half of the protein and an extraordinary replacement/silent ratio of nucleotide changes in a narrow region surrounding the reactive site. The clustering of polymorphisms near the reactive site combined with the high replacement/silent ratio suggests an evolutionary mechanism that apparently selects for functional diversity of the alpha-1-PI genes. Finally, modeling of the three-dimensional position of the alpha-1-PI polymorphic residues into the homologous positions of the crystallographic structure of ovalbumin, a member of the alpha-1-PI supergene family, predicts that many of these amino acids are on the surfaces, which are likely to interact with the protease targets.