Protein CGL2373 from Corynebacterium glutamicum was previously proposed to be a member of the polyketide_cyc2 family, based on amino-acid sequence and secondary structure features derived from NMR chemical shift assignments. We report here the solution NMR structure of CGL2373, which contains three α-helices and one antiparallel β-sheet and adopts a helix-grip fold. This structure shows moderate similarities to the representative polyketide cyclases, TcmN, WhiE, and ZhuI. Nevertheless, unlike the structures of these homologs, CGL2373 structure looks like a half-open shell with a much larger pocket, and key residues in the representative polyketide cyclases for binding substrate and catalyzing aromatic ring formation are replaced with different residues in CGL2373. Also, the gene cluster where the CGL2373-encoding gene is located in C. glutamicum contains additional genes encoding nucleoside diphosphate kinase, folylpolyglutamate synthase, and valine-tRNA ligase, different from the typical gene cluster encoding polyketide cyclase in Streptomyces. Thus, although CGL2373 is structurally a polyketide cyclase-like protein, the function of CGL2373 may differ from the known polyketide cyclases and needs to be further investigated. The solution structure of CGL2373 lays a foundation for in silico ligand screening and binding site identifying in future functional study.

中文翻译：

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谷氨酸棒杆菌的聚酮化合物环化酶样蛋白CGL2373的溶液NMR结构。

基于氨基酸序列和源自NMR化学位移分配的二级结构特征，先前提出了谷氨酸棒杆菌的CGL2373蛋白是polyketide_cyc2家族的成员。我们在这里报告CGL2373的溶液NMR结构，其中包含三个α-螺旋和一个反平行的β-折叠，并采用了螺旋-握持折叠。该结构显示出与代表性聚酮化合物环化酶TcmN，WhiE和ZhuI的适度相似性。然而，与这些同源物的结构不同，CGL2373的结构看起来像是一个半开的外壳，具有更大的口袋，并且代表性的聚酮环化酶中用于结合底物和催化芳香环形成的关键残基被CGL2373中的不同残基取代。另外，CGL2373编码基因所在的基因簇位于C中。谷氨酸含有编码核苷二磷酸激酶，叶酰聚谷氨酸合酶和缬氨酸-tRNA连接酶的其他基因，与链霉菌中编码聚酮化合物环化酶的典型基因簇不同。因此，尽管CGL2373在结构上是聚酮化合物环化酶样蛋白，但CGL2373的功能可能不同于已知的聚酮化合物环化酶，需要进一步研究。CGL2373的溶液结构为将来的功能研究进行计算机配体筛选和结合位点识别奠定了基础。CGL2373的功能可能不同于已知的聚酮化合物环化酶，需要进一步研究。CGL2373的溶液结构为将来的功能研究进行计算机配体筛选和结合位点鉴定奠定了基础。CGL2373的功能可能不同于已知的聚酮环化酶，需要进一步研究。CGL2373的溶液结构为将来的功能研究进行计算机配体筛选和结合位点鉴定奠定了基础。