Bertelsen A H, Beaudry G A, Galella E A, Jones B N, Ray M L, Mehta N M
Unigene Laboratories, Inc., Fairfield, New Jersey 07006.
Arch Biochem Biophys. 1990 May 15;279(1):87-96. doi: 10.1016/0003-9861(90)90466-c.
The alpha-amidating enzyme activity in rat medullary thyroid carcinoma (MTC) consists of multiple, active enzymes that can be resolved by ion-exchange chromatography. Amino acid sequences from one form of purified rat MTC alpha-amidating enzyme have been utilized to design oligonucleotide probes for isolating cDNAs encoding this protein. Sequence analysis of multiple cDNA clones indicates that there are at least two types of cDNA in rat tissues. These cDNAs differ primarily by the absence (type A) or the presence (type B) of a 315-base internal sequence. Additional heterogeneity in the 3' coding regions of the different mRNAs has also been found. Both types of cDNA predict primary translation products that are preproenzymes which must be post-translationally processed at both their amino and carboxyl termini. Sequence analysis of the purified peak III protein from rat MTC demonstrates that the type A mRNA encodes this 75-kDa protein. This analysis also provides support for the assignment of the C-terminal processing site. In addition, data are presented which demonstrate that type B mRNA is also functional. The implications of the internal and carboxyl-end heterogeneity are discussed.
大鼠甲状腺髓样癌（MTC）中的α-酰胺化酶活性由多种活性酶组成，这些酶可通过离子交换色谱法分离。已利用一种纯化的大鼠MTCα-酰胺化酶的氨基酸序列设计寡核苷酸探针，用于分离编码该蛋白的cDNA。多个cDNA克隆的序列分析表明，大鼠组织中至少存在两种类型的cDNA。这些cDNA的主要区别在于是否存在一个315个碱基的内部序列（A型不存在，B型存在）。在不同mRNA的3'编码区也发现了其他异质性。两种类型的cDNA都预测初级翻译产物是前体酶，必须在其氨基和羧基末端进行翻译后加工。对大鼠MTC纯化的峰III蛋白的序列分析表明，A型mRNA编码这种75 kDa的蛋白。该分析还为C末端加工位点的确定提供了支持。此外，还提供了数据表明B型mRNA也具有功能。讨论了内部和羧基末端异质性的影响。
