Zhang L, Jenkins K P, Stutz E, Hallick R B
Department of Biochemistry, University of Arizona, Tucson 85721, USA.
RNA. 1995 Dec;1(10):1079-88.
The 4,144 nt Euglena gracilis chloroplast psbC intron 2 has been characterized as a single, cis-spliced 593 nt group II intron interrupted by an open reading frame of 758 codons in the loop region of domain IV. The 2,277 nt coding region of orf 758 is interrupted by two additional group II introns of 369 nt and 352 nt. Another 553 nt group II intron is located in the 5' untranslated leader region of orf 758. Because the psbC intron 2 orf encodes a maturase-like protein that has reverse transcriptase domains and a domain X characteristic of group II intron-encoded proteins, the locus has been designated mat2. The psbC intron 2 is the first member of a new category of twintron, characterized by introns within a gene within another intron. A potential role of psbC intron 2 as a "founder" intron involved in the spread of introns to new sites in the plastid genome of the Euglenophycae is discussed.
纤细裸藻叶绿体psbC内含子2长度为4144个核苷酸，其特征为一个单一的、顺式剪接的593个核苷酸的II类内含子，在结构域IV的环区域被一个758个密码子的开放阅读框中断。orf 758的2277个核苷酸编码区域被另外两个分别为369个核苷酸和352个核苷酸的II类内含子中断。另一个553个核苷酸的II类内含子位于orf 758的5'非翻译前导区域。由于psbC内含子2的orf编码一种具有逆转录酶结构域和II类内含子编码蛋白特征性结构域X的成熟酶样蛋白，该基因座被命名为mat2。psbC内含子2是一种新型双内含子的首个成员，其特征是在另一个内含子中的基因内存在内含子。本文讨论了psbC内含子2作为“奠基者”内含子在将内含子传播到裸藻门质体基因组新位点中所起的潜在作用。
