Hagenbüchle O, Bovey R, Young R A
Cell. 1980 Aug;21(1):179-87. doi: 10.1016/0092-8674(80)90125-7.
We have determined the nucleotide sequence of two different mouse alpha-amylase mRNAs, one found in the pancreas and the other in the salivary gland. The 1577 and 1659 nucleotide mRNAs from pancreas and salivary gland, respectively are the major alpha-amylase species which accumulate in each tissue. Differences in mRNA length are primarily in the 5' noncoding regions. Comparable portions of the mRNAs are 89% homologous. The mRNA sequences predict alpha-amylase precursor proteins of 508 and 511 amino acid residues, accounting for nearly the entire coding capacity of the mRNAs; differences in protein length occur as a result of a nine nucleotide segment present within the translated portion of salivary gland, but not pancreas, mRNA. The lengths and amino acid compositions of the predicted proteins concur with those determined empirically by others. These proteins differ 12% in amino acid sequence, explaining previously observed differences in net charge and antigenic properties. Finally, translation of the salivary gland alpha-amylase mRNA is not initiated at the AUG codon nearest the 5' terminus since that codon is almost immediately followed by the termination triplet UAA. This observation may have implications for the mechanism of translation initiation in eucaroytes.
我们已经确定了两种不同的小鼠α-淀粉酶mRNA的核苷酸序列，一种存在于胰腺中，另一种存在于唾液腺中。来自胰腺和唾液腺的1577个核苷酸和1659个核苷酸的mRNA分别是在每个组织中积累的主要α-淀粉酶种类。mRNA长度的差异主要在5'非编码区。mRNA的可比部分有89%的同源性。mRNA序列预测α-淀粉酶前体蛋白分别有508和511个氨基酸残基，几乎占了mRNA的全部编码能力；蛋白质长度的差异是由于唾液腺mRNA（而非胰腺mRNA）翻译部分中存在一个9个核苷酸的片段。预测蛋白质的长度和氨基酸组成与其他人通过实验确定的结果一致。这些蛋白质的氨基酸序列有12%的差异，解释了之前观察到的净电荷和抗原特性的差异。最后，唾液腺α-淀粉酶mRNA的翻译不是从最靠近5'末端的AUG密码子开始的，因为该密码子几乎紧接着终止三联体UAA。这一观察结果可能对真核生物的翻译起始机制有影响。
