Mikkonen M, Alatossava T
Department of Genetics, University of Oulu, Finland.
Microbiology (Reading). 1995 Sep;141 ( Pt 9):2183-90. doi: 10.1099/13500872-141-9-2183.
An 837 nt long group IA intron was discovered in the Lactobacillus delbrueckii subsp. lactis virulent phage LL-H genome. The LL-H intron conforms well to the secondary structure that is common to all group I introns. The only exception is that the extreme 3' nucleotide of the intron is an A residue instead of the usual G; despite this the intron is efficiently spliced in vivo. This LL-H intron contains an ORF, ORF168, which shows homology with endonucleases encoded by ORFs contained in Bacillus subtilis phage introns. At present, the LL-H intron is the only one found in the phages of lactic acid bacteria and the first one to be found in a phage belonging to the most abundant taxonomic group, group B or Siphoviridae. The LL-H intron interrupts gene terL, the product of which (50.5 kDa, TerL) is significantly homologous to the large subunit of B. subtilis phage SPP1 terminase. The product of the upstream gene, terS of LL-H (15.9 kDa, TerS), shows homology to small subunits of B. subtilis phage terminases.
在德氏乳杆菌保加利亚亚种烈性噬菌体LL-H基因组中发现了一个长度为837 nt的IA组内含子。LL-H内含子与所有I组内含子共有的二级结构高度契合。唯一的例外是，内含子最末端的3'核苷酸是A残基而非通常的G；尽管如此，该内含子在体内仍能高效剪接。这个LL-H内含子包含一个开放阅读框ORF168，它与枯草芽孢杆菌噬菌体内含子中所含开放阅读框编码的内切核酸酶具有同源性。目前，LL-H内含子是在乳酸菌噬菌体中发现的唯一内含子，也是在属于最丰富分类群B组或长尾噬菌体科的噬菌体中发现的首个内含子。LL-H内含子中断了基因terL，其产物（50.5 kDa，TerL）与枯草芽孢杆菌噬菌体SPP1末端酶的大亚基具有显著同源性。LL-H上游基因terS的产物（15.9 kDa，TerS）与枯草芽孢杆菌噬菌体末端酶的小亚基具有同源性。
