Gehring M R, Shiels B R, Northemann W, de Bruijn M H, Kan C C, Chain A C, Noonan D J, Fey G H
J Biol Chem. 1987 Jan 5;262(1):446-54.
Six alpha 2-macroglobulin cDNA clones were isolated from two liver cDNA libraries produced from rats undergoing acute inflammation. The coding sequence for rat alpha 2-macroglobulin including its 27-residue signal peptide and the 3' - and part of the 5' nontranslated regions were determined. The mature protein consisting of 1445 amino acids is coded for by a 4790 +/- 40 nucleotide messenger RNA. It contains a typical internal thiol ester region and 25 cysteine residues which are conserved between rat and human alpha 2-macroglobulin. Although the amino acid sequences of rat and human alpha 2-macroglobulin share 73% identity, two small divergent areas of 17 and 38 residues were found, corresponding to 29 and 11% identity, respectively. These areas are located in the bait region and, therefore, may confer specific proteinase recognition capabilities on rat alpha 2-macroglobulin. Following an inflammatory stimulation, rat alpha 2-macroglobulin mRNA levels increased 214-fold over control values and reached a maximum at 18 h. By 24 h the levels had decreased to less than 30% of the maximum value. Transcription rates from the alpha 2-macroglobulin gene as measured in nuclear run-on experiments showed a less than 3-fold increase in nuclei from acutely inflamed rats as compared to controls. These results suggest that the accummulation of alpha 2M mRNA is due to the combined effects of increased transcription rates and post-transcriptional processing.
从两个由急性炎症大鼠肝脏构建的cDNA文库中分离出六个α2-巨球蛋白cDNA克隆。测定了大鼠α2-巨球蛋白的编码序列，包括其27个氨基酸残基的信号肽以及3'非翻译区和部分5'非翻译区。由1445个氨基酸组成的成熟蛋白由一个4790±40个核苷酸的信使RNA编码。它包含一个典型的内部硫酯区域和25个半胱氨酸残基，这些残基在大鼠和人α2-巨球蛋白之间是保守的。尽管大鼠和人α2-巨球蛋白的氨基酸序列有73%的同一性，但发现了两个小的差异区域，分别由17个和38个残基组成，同一性分别为29%和11%。这些区域位于诱饵区，因此可能赋予大鼠α2-巨球蛋白特定的蛋白酶识别能力。在炎症刺激后，大鼠α2-巨球蛋白mRNA水平比对照值增加了214倍，并在18小时达到最大值。到24小时，水平已降至最大值的30%以下。在核转录实验中测定的α2-巨球蛋白基因的转录率显示，与对照相比，急性炎症大鼠细胞核中的转录率增加不到3倍。这些结果表明，α2M mRNA的积累是转录率增加和转录后加工共同作用的结果。
