文章基本信息

标题：Methylofuran is a prosthetic group of the formyltransferase/hydrolase complex and shuttles one-carbon units between two active sites
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作者：Jethro L. Hemmann ; Tristan Wagner ; Seigo Shima 等
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2019
卷号：116
期号：51
页码：25583-25590
DOI：10.1073/pnas.1911595116
出版社：The National Academy of Sciences of the United States of America
摘要：Methylotrophy, the ability of microorganisms to grow on reduced one-carbon substrates such as methane or methanol, is a feature of various bacterial species. The prevailing oxidation pathway depends on tetrahydromethanopterin (H₄MPT) and methylofuran (MYFR), an analog of methanofuran from methanogenic archaea. Formyltransferase/hydrolase complex (Fhc) generates formate from formyl-H₄MPT in two consecutive reactions where MYFR acts as a carrier of one-carbon units. Recently, we chemically characterized MYFR from the model methylotroph Methylorubrum extorquens and identified an unusually long polyglutamate side chain of up to 24 glutamates. Here, we report on the crystal structure of Fhc to investigate the function of the polyglutamate side chain in MYFR and the relatedness of the enzyme complex with the orthologous enzymes in archaea. We identified MYFR as a prosthetic group that is tightly, but noncovalently, bound to Fhc. Surprisingly, the structure of Fhc together with MYFR revealed that the polyglutamate side chain of MYFR is branched and contains glutamates with amide bonds at both their α- and γ-carboxyl groups. This negatively charged and branched polyglutamate side chain interacts with a cluster of conserved positively charged residues of Fhc, allowing for strong interactions. The MYFR binding site is located equidistantly from the active site of the formyltransferase (FhcD) and metallo-hydrolase (FhcA). The polyglutamate serves therefore an additional function as a swinging linker to shuttle the one-carbon carrying amine between the two active sites, thereby likely increasing overall catalysis while decreasing the need for high intracellular MYFR concentrations.
关键词：methylotrophy ; one-carbon metabolism ; coenzyme ; prosthetic group ; polyglutamate