Ogawa T, Oda N, Nakashima K, Sasaki H, Hattori M, Sakaki Y, Kihara H, Ohno M
Department of Chemistry, Faculty of Science, Kyushu University, Fukuoka, Japan.
Proc Natl Acad Sci U S A. 1992 Sep 15;89(18):8557-61. doi: 10.1073/pnas.89.18.8557.
As a step toward understanding the structure and function of phospholipases A2 (PLA2s), we isolated and sequenced several cDNAs encoding Trimeresurus flavoviridis venom PLA2 isozymes including two [Lys49]PLA2s called basic proteins I and II, [Thr37]PLA2, and PLX'-PLA2. Comparison of the nucleotide sequences of these cDNAs with the previously isolated [Asp49]PLA2 cDNA revealed some interesting findings from the viewpoint of evolution. First, the homologies of the 5' and 3' untranslated regions (98% and 89%, respectively) were much higher than that of the protein-coding regions (67%). The predicted secondary structure showed the characteristic stem-loop structures for both the untranslated regions of the mRNAs, suggesting that these regions play some functional role(s) in translation or stability of mRNAs. Second, base substitutions appeared to have occurred at similar rates for the three positions of codons among these PLA2s. The results are discussed in terms of evolution of PLA2s. Northern blot analysis showed that these PLA2s are specific to venom gland.
作为了解磷脂酶A2（PLA2s）结构和功能的一个步骤，我们分离并测序了几个编码竹叶青蛇毒PLA2同工酶的cDNA，包括两种称为碱性蛋白I和II的[Lys49]PLA2、[Thr37]PLA2和PLX'-PLA2。将这些cDNA的核苷酸序列与先前分离的[Asp49]PLA2 cDNA进行比较，从进化的角度揭示了一些有趣的发现。首先，5'和3'非翻译区的同源性（分别为98%和89%）远高于蛋白质编码区的同源性（67%）。预测的二级结构显示了mRNA非翻译区的特征性茎环结构，表明这些区域在mRNA的翻译或稳定性中发挥了某些功能作用。其次，这些PLA2中密码子的三个位置似乎以相似的速率发生碱基替换。根据PLA2s的进化对结果进行了讨论。Northern印迹分析表明，这些PLA2对毒腺具有特异性。
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