Institute of Biotechnology, University of Helsinki, P.O. Box 65, FIN-00014 Helsinki, Finland.
Basic Science Program, Frederick National Laboratory for Cancer Research, Frederick, MD 21702, USA.
Int J Mol Sci. 2020 Nov 7;21(21):8367. doi: 10.3390/ijms21218367.
Protein splicing catalyzed by inteins utilizes many different combinations of amino-acid types at active sites. Inteins have been classified into three classes based on their characteristic sequences. We investigated the structural basis of the protein splicing mechanism of class 3 inteins by determining crystal structures of variants of a class 3 intein from and molecular dynamics simulations, which suggested that the class 3 intein utilizes a different splicing mechanism from that of class 1 and 2 inteins. The class 3 intein uses a bond cleavage strategy reminiscent of proteases but share the same Hedgehog/INTein (HINT) fold of other intein classes. Engineering of class 3 inteins from a class 1 intein indicated that a class 3 intein would unlikely evolve directly from a class 1 or 2 intein. The HINT fold appears as structural and functional solution for -peptidyl and -esterification reactions commonly exploited by diverse mechanisms using different combinations of amino-acid types for the active-site residues.
蛋白质剪接由内肽酶催化，在活性位点利用许多不同类型的氨基酸组合。根据其特征序列，内肽酶被分为三类。我们通过确定来自和分子动力学模拟的 3 类内肽酶变体的晶体结构，研究了 3 类内肽酶的蛋白质剪接机制的结构基础，这表明 3 类内肽酶利用与 1 类和 2 类内肽酶不同的剪接机制。3 类内肽酶使用类似于蛋白酶的键断裂策略，但与其他内肽酶类别的 Hedgehog/INTein (HINT) 折叠相同。来自 1 类内肽酶的 3 类内肽酶的工程表明，3 类内肽酶不太可能直接从 1 类或 2 类内肽酶进化而来。HINT 折叠似乎是一种结构和功能解决方案，用于 -肽和 -酯化反应，这些反应通常通过不同的氨基酸类型组合利用不同的机制来共同利用。
