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首页> 外文期刊>Journal of Molecular Biology >Crystal Structures of an Intein from the Split dnaE Gene of Synechocystis sp. PCC6803 Reveal the Catalytic Model Without the Penultimate Histidine and the Mechanism of Zinc Ion Inhibition of Protein Splicing.
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Crystal Structures of an Intein from the Split dnaE Gene of Synechocystis sp. PCC6803 Reveal the Catalytic Model Without the Penultimate Histidine and the Mechanism of Zinc Ion Inhibition of Protein Splicing.

机译：分离的Synechocystis sp。的dnaE基因的内含肽的晶体结构。 PCC6803揭示了没有倒数第二个组氨酸的催化模型和锌离子抑制蛋白剪接的机理。

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The first naturally occurring split intein was found in the dnaE gene of Synechocystis sp. PCC6803 and belongs to a subclass of inteins without a penultimate histidine residue. We describe two high-resolution crystal structures, one derived from an excised Ssp DnaE intein and the second from a splicing-deficient precursor protein. The X-ray structures indicate that His147 in the conserved block F activates the side-chain N(delta) atom of the intein C-terminal Asn159, leading to a nucleophilic attack on the peptide bond carbonyl carbon atom at the C-terminal splice site. In this process, Arg73 appears to stabilize the transition state by interacting with the carbonyl oxygen atom of the scissile bond. Arg73 also seems to substitute for the conserved penultimate histidine residue in the formation of an oxyanion hole, as previously identified in other inteins. The finding that the precursor structure contains a zinc ion chelating the highly conserved Cys160 and Asp140 reveals the structural basis of Zn(2+)-mediated inhibition of protein splicing. Furthermore, it is of interest to observe that the carbonyl carbon atom of Asn159 and N(eta) of Arg73 are 2.6A apart in the free intein structure and 10.6A apart in the precursor structure. The orientation change of the aromatic ring of Tyr-1 following the initial acyl shift may be a key switching event contributing to the alignment of Arg73 and the C-terminal scissile bond, and may explain the sequential reaction property of the Ssp DnaE intein.
机译：在Synechocystis sp。的dnaE基因中发现了第一个自然发生的分裂内含子。 PCC6803属于inteins的一个子类，没有倒数第二个组氨酸残基。我们描述了两个高分辨率的晶体结构，一个来自一个被切除的Ssp DnaE内含子，第二个来自一个剪接缺陷的前体蛋白。 X射线结构表明保守区F中的His147激活内含蛋白C端Asn159的侧链Nδ原子，导致对C端剪接位点的肽键羰基碳原子的亲核攻击。在此过程中，Arg73似乎通过与易裂键的羰基氧原子相互作用而稳定了过渡态。 Arg73似乎在氧阴离子孔的形成中也可以替代保守的倒数第二个组氨酸残基，如先前在其他蛋白中所鉴定的。前体结构包含一个锌离子螯合高度保守的Cys160和Asp140的发现揭示了Zn（2+）介导的蛋白剪接抑制的结构基础。此外，令人感兴趣的是，观察到Asn159的羰基碳原子和Arg73的N（eta）在游离内含肽结构中相距2.6A，在前体结构中相距10.6A。最初的酰基转移后，Tyr-1芳香环的取向变化可能是一个关键的转换事件，有助于Arg73和C端易裂键的排列，并可以解释Ssp DnaE内含肽的顺序反应特性。

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