犬载脂蛋白C-II和C-III mRNA的结构与表达。对载脂蛋白结构的进化及功能限制的启示。

Structure and expression of dog apolipoprotein C-II and C-III mRNAs. Implications for the evolution and functional constraints of apolipoprotein structure.

作者信息

Datta S, Li W H, Ghosh I, Luo C C, Chan L

出版信息

J Biol Chem. 1987 Aug 5;262(22):10588-93.

Abstract

The complete cDNAs for canine apolipoprotein (apo) C-II and C-III have been cloned in the plasmid vector, pUC-18, and the phage vector, lambda gt11. With 32P-labeled nick-translated cDNAs as hybridization probes, apoC-II and apoC-III mRNAs were found to be expressed in canine liver, jejunum, ileum, colon, pancreas, spleen, ovary, and bladder at the following relative concentrations: 100, 35, 30, 10, 15, 5, 30, and 2% for apoC-II, and 100, 35, 15, 2, 20, 5, 30, and 5% for apoC-III. Neither mRNA was detected in canine brain, kidney, lung, muscle, oviduct, uterus, or testis. Both mRNAs are approximately 700 nucleotides in length. Complete sequence analysis revealed that apoC-II mRNA codes for a protein of 101 amino acid residues including 22 residues in the signal peptide and 79 residues in the mature peptide region. ApoC-III mRNA codes for a protein of 100 amino acid residues, including 20 in the signal peptide and 80 residues in the mature peptide region. It contains a single cysteine residue in position 54. Secondary structural analysis shows the presence of two regions each of amphipathic helix for apoC-II (residues 14-33 and 44-63) and apoC-III (residues 16-33 and 50-69). Computer analysis of the amphipathic helical regions demonstrates the importance of variation in the dihedral angles of the side chains in the charge microenvironment of the helices. Statistical analysis of sequence similarities between human apoC-II, apoC-III, apoA-II, apoA-I, apoE, and apoA-IV, and dog apoC-II and apoC-III, and rat apoC-III, apoA-II, apoA-I, apoE, and apoA-IV indicates that all these proteins have evolved rapidly, especially in the rat in which apoC-III has evolved at three times the rate in man and dog. Further, the shorter apolipoproteins, apoA-II, apoC-II, and a-poC-III, have evolved more rapidly than the longer ones, apoA-I, apoE, and apoA-IV. Some regions in the individual apolipoproteins are better conserved than others. The rate of evolution of individual regions seems to be related to the stringency of their functional requirements.

摘要

犬载脂蛋白（apo）C-II和C-III的全长cDNA已被克隆到质粒载体pUC-18和噬菌体载体λgt11中。以32P标记的缺口平移cDNA作为杂交探针，发现apoC-II和apoC-III mRNA在犬的肝脏、空肠、回肠、结肠、胰腺、脾脏、卵巢和膀胱中表达，其相对浓度如下：apoC-II分别为100%、35%、30%、10%、15%、5%、30%和2%；apoC-III分别为100%、35%、15%、2%、20%、5%、30%和5%。在犬的脑、肾、肺、肌肉、输卵管、子宫或睾丸中均未检测到这两种mRNA。两种mRNA的长度均约为700个核苷酸。完整的序列分析表明，apoC-II mRNA编码一种由101个氨基酸残基组成的蛋白质，其中信号肽有22个残基，成熟肽区域有79个残基。apoC-III mRNA编码一种由100个氨基酸残基组成的蛋白质，其中信号肽有20个残基，成熟肽区域有80个残基。它在第54位含有一个半胱氨酸残基。二级结构分析表明，apoC-II（第14 - 33位和44 - 63位残基）和apoC-III（第16 - 33位和50 - 69位残基）各有两个两亲性螺旋区域。对两亲性螺旋区域的计算机分析表明，侧链二面角的变化在螺旋电荷微环境中具有重要意义。对人apoC-II、apoC-III、apoA-II、apoA-I、apoE和apoA-IV，犬apoC-II和apoC-III，以及大鼠apoC-III、apoA-II、apoA-I、apoE和apoA-IV之间序列相似性的统计分析表明，所有这些蛋白质都进化得很快，尤其是在大鼠中，其中apoC-III的进化速度是人和犬的三倍。此外，较短的载脂蛋白apoA-II、apoC-II和apoC-III比较长的载脂蛋白apoA-I、apoE和apoA-IV进化得更快。单个载脂蛋白中的某些区域比其他区域保守性更好。单个区域的进化速度似乎与其功能要求的严格程度有关。