狗肝脏苯甲二氮茸结合抑制因子的cDNA克隆及序列分析

在研究狗抗吗啡活性肽ＰＰＣ过程中，发现它与牛的ＤＢＩ（ｄｉａｚｅｐａｍｂｉｎｄｉｎｇｉｎｈｉｂｉｔｏｒ）的氨基酸序列有很高的同源性，但尚未见到有关狗的ＤＢＩ的文献报道，为了更好的探讨ＰＰＣ和ＤＢＩ相互间的关系，对狗的ＤＢＩ的ｃＤＮＡ进行了克隆和序列分析。本研究利用大鼠ＤＢＩ的基因片段为探针，从狗肝脏ｃＤＮＡ文库中，筛选得到了一阳性克隆，并进行了全自动和手工测序，得到了ＤＢＩ的全长基因。根据ＥＢＭＬｂａｎｋ序列检索，发现狗的ＤＢＩ核酸序列与牛的同源性为８１％，将其核酸序列翻译成氨基酸序列，进行同源序列比较，结果显示：狗的ＤＢＩ的氨基酸序列与猪、牛、人、酵母ＤＢＩ的同源性分别为８８．５％、８７．４％、８３．９％、４６．５％。研究还发现狗的ＤＢＩ序列与抗吗啡活性肽ＰＰＣＮ端６２个氨基酸只有两个不同，Ｃ端１７个氨基酸序列完全相同。只是ＰＰＣ比ＤＢＩ中间多了２３个氨基酸。

Cloning and Sequencing of cDNA Encoding the Diazepam Binding Inhibitor (DBI)

The anti morphine peptide PPC from dog brain has an inhibitory effect on morphine analgesia. It is highly homologous to DBI. The analgesic effect of bovine DBI was measured, showing the potentiation effect on morphine analgesia . In order to study the relationship between PPC and DBI , cDNA library derived from dog liver had been screened using partial gene of rat DBI as a probe. A positive clone was obtained. The entire sequence of the insert of this positive clone provided complete sequence of a peptide which was identified as the DBI peptide. It shows 88.5% homology with pig DBI, 87.4% with bovine, 83.9% with human, 46.5% with yeast ,respectively. The sequence of N terminal 50 amino acid residues except 55th, 58th site and C terminal 17 amino acids is the same to DBI from dog. PPC has 23 amino acids more than DBI inside.