Emrie P A, Shannon J M, Mason R J, Fisher J H
Department of Medicine, National Jewish Center for Immunology and Respiratory Medicine, Denver, CO 80206.
Biochim Biophys Acta. 1989 Feb 23;994(3):215-21. doi: 10.1016/0167-4838(89)90296-3.
Pulmonary surfactant prevents collapse of lung alveoli by lowering surface tension at the air/liquid interface. The hydrophobic surfactant associated proteins SP-B and SP-C have been shown to be important in surfactant function and metabolism. A cDNA clone for rat SP-B was isolated and sequenced. Northern analysis showed mRNA for SP-B was present in whole lung and was greatly enriched in alveolar type II cells, but was not present in brain, kidney, spleen or liver. A full length transcript of the rat SP-B cDNA clone consists of 1536 bases and encodes an open reading frame of 376 amino acids. The predicted molecular mass of the primary translation product is 42 kDa and the predicted molecular mass of the mature protein is 8 kDa. Extensive homology exists between the rat sequence for SP-B and those reported for human and canine SP-B. The position of 25 cysteine residues has been extremely well preserved across all three species. An N-linked glycosylation site in the COOH region has been conserved across all three species. A search of the NIH database revealed homology between rat SP-B and the active site for the mouse contrapsin serum proteinase inhibitor.
肺表面活性物质通过降低气/液界面的表面张力来防止肺泡塌陷。疏水性表面活性物质相关蛋白SP-B和SP-C已被证明在表面活性物质的功能和代谢中起重要作用。分离并测序了大鼠SP-B的cDNA克隆。Northern分析表明，SP-B的mRNA存在于全肺中，在II型肺泡细胞中大量富集，但在脑、肾、脾或肝脏中不存在。大鼠SP-B cDNA克隆的全长转录本由1536个碱基组成，编码一个376个氨基酸的开放阅读框。初级翻译产物的预测分子量为42 kDa，成熟蛋白的预测分子量为8 kDa。大鼠SP-B序列与已报道的人及犬SP-B序列之间存在广泛的同源性。在所有三个物种中，25个半胱氨酸残基的位置都保存得非常好。COOH区域的一个N-连接糖基化位点在所有三个物种中都保守。对美国国立卫生研究院数据库的搜索揭示了大鼠SP-B与小鼠抗胰蛋白酶血清蛋白酶抑制剂活性位点之间的同源性。
