Institute of Biological Sciences and Biotechnology, Donghua University, Shanghai, PR China.
FEBS Lett. 2011 Aug 4;585(15):2513-8. doi: 10.1016/j.febslet.2011.06.035. Epub 2011 Jul 5.
Previously, the C-terminal fragment of a split intein was known to undergo controllable C-cleavage at its C-terminus only when the N-terminal fragment of the intein was added. Here we constructed a similar split intein from the Ssp DnaX intein, but we unexpectedly observed that its C-terminal 136-aa fragment could undergo spontaneous C-cleavage without the N-terminal fragment that was up to 15 aa long and contained the conserved intein motif A. This C-cleavage activity was significantly decreased by a mutation of the conserved Thr residue in the conserved intein motif B. These findings suggest a robust intein structure in the absence of motif A and a larger role of motif B in the third step of the protein splicing mechanism.
先前，仅当带有内含肽 N 端片段存在时，分裂内含肽的 C 端片段才会在其 C 端发生可控的 C 裂解。在这里，我们构建了一个来自 Ssp DnaX 内含肽的类似分裂内含肽，但我们出人意料地观察到其 C 端 136-残基片段可以在没有长达 15 个残基并包含保守内含肽模体 A 的 N 端片段的情况下自发发生 C 裂解。该 C 裂解活性通过保守内含肽模体 B 中保守 Thr 残基的突变而显著降低。这些发现表明在没有模体 A 的情况下内含肽结构坚固，以及模体 B 在蛋白质剪接机制的第三步中起更大的作用。
