New England Biolabs, Inc., Ipswich, Massachusetts, United States of America.
PLoS One. 2011;6(10):e26361. doi: 10.1371/journal.pone.0026361. Epub 2011 Oct 18.
An Arthrobacter species FB24 gene (locus tag Arth_1007) was previously annotated as a putative intein-containing DnaB helicase of phage origin (Arsp-FB24 DnaB intein). However, it is not a helicase gene because the sequence similarity is limited to inteins. In fact, the flanking exteins total only 66 amino acids. Therefore, the intein should be referred to as the Arsp-FB24 Arth_1007 intein. The Arsp-FB24 Arth_1007 intein failed to splice in its native precursor and in a model precursor. We previously noted that the Arsp-FB24 Arth_1007 intein is the only putative Class 3 intein that is missing the catalytically essential Cys at position 4 of intein Motif F, which is one of the three defining signature residues of this class. Additionally, a catalytically essential His in position 10 of intein Motif B is also absent; this His is the most conserved residue amongst all inteins. Splicing activity was not rescued when these two catalytically important positions were 'reverted' back to their consensus residues. This study restores the unity of the Class 3 intein signature sequence in active inteins by demonstrating that the Arsp-FB24 Arth_1007 intein is an inactive pseudogene.
先前，一种节杆菌属（Arthrobacter） FB24 基因（基因座标签 Arth_1007）被注释为噬菌体来源的假定内含肽 DnaB 解旋酶（Arsp-FB24 DnaB 内含肽）。然而，由于序列相似性仅限于内含肽，该基因并非解旋酶基因。事实上，侧翼外显子总共只有 66 个氨基酸。因此，该内含肽应被称为 Arsp-FB24 Arth_1007 内含肽。Arsp-FB24 Arth_1007 内含肽未能在其天然前体和模型前体中进行剪接。我们先前注意到，Arsp-FB24 Arth_1007 内含肽是唯一缺失内含肽 motif F 第 4 位催化必需 Cys 的假定 Class 3 内含肽，而 motif F 是该类别的三个定义特征残基之一。此外，内含肽 motif B 第 10 位的催化必需 His 也不存在；该 His 是所有内含肽中最保守的残基。当这两个催化重要位置“恢复”为其保守残基时，剪接活性并未恢复。通过证明 Arsp-FB24 Arth_1007 内含肽是一种无活性的假基因，本研究恢复了活性内含肽的 Class 3 内含肽特征序列的统一性。
