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长期以来,插入序列一直被视为真核类基因的标记。最近人们在一个编码蛋白质的原核类基因中发现了插入序列(或叫内含子)。这一内含子把T4噬菌体胸腺嘧啶核苷酸合成酶的编码序列,分离成两个外显子。外显子Ⅰ编码胸腺嘧啶核苷酸合成酶N末端的183个氨基酸;外显子Ⅱ编码其余103个氨基酸。该内含子长度为1017个核苷酸,以ochre终止密码子开头,以ATG(一种潜在的起始密码子)结束。这些密码子的出现使人们推测T4噬菌体感染时,胸腺嘧啶核苷酸合成酶的合成可能利用一种前所未有的多肽链连接反应;或者,通过一种尚未发现的原核类mRNA加工系统来完成。
For a long time, the insertion sequence has been regarded as a marker of eukaryotic genes. Recently, an insertion sequence (or intron) was found in a prokaryotic gene encoding a protein. This intron separates the T4 phage thymine nucleotide synthetase coding sequence into two exons. Exon 1 encodes 183 amino acids at the N-terminus of thymidine synthase; exon II encodes the remaining 103 amino acids. This intron is 1017 nucleotides in length, beginning with the ochre stop codon and ending with ATG, a potential start codon. The advent of these codons has led to speculation that the T4 thymidine synthase synthesis may utilize an unprecedented polypeptide chain ligation reaction when T4 bacteriophage is infected or by an undiscovered prokaryotic mRNA processing system.