5,10-methenyltetrahydromethanopterin 在
5,10-methenyltetrahydromethanopterin hydrogenase II from Methanocaldococcus jannaschii holo type 、 氢气 作用下,
以
aq. phosphate buffer 为溶剂,
生成 5,10-methylenetetrahydromethanopterin
参考文献:
名称:
Towards a functional identification of catalytically inactive [Fe]‐hydrogenase paralogs
摘要:
[Fe]‐hydrogenase (Hmd), an enzyme of the methanogenic energy metabolism, harbors an iron‐guanylylpyridinol (FeGP) cofactor used for H2 cleavage. The generated hydride is transferred to methenyl‐tetrahydromethanopterin (methenyl‐H4MPT+). Most hydrogenotrophic methanogens contain the hmd‐related genes hmdII and hmdIII. Their function is still elusive. We were able to reconstitute the HmdII holoenzyme of Methanocaldococcus jannaschii with recombinantly produced apoenzyme and the FeGP cofactor, which is a prerequisite for in vitro functional analysis. Infrared spectroscopic and X‐ray structural data clearly indicated binding of the FeGP cofactor. Methylene‐H4MPT binding was detectable in the significantly altered infrared spectra of the HmdII holoenzyme and in the HmdII apoenzyme–methylene‐H4MPT complex structure. The related binding mode of the FeGP cofactor and methenyl‐H4MPT+ compared with Hmd and their multiple contacts to the polypeptide highly suggest a biological role in HmdII. However, holo‐HmdII did not catalyze the Hmd reaction, not even in a single turnover process, as demonstrated by kinetic measurements. The found inactivity can be rationalized by an increased contact area between the C‐ and N‐terminal folding units in HmdII compared with in Hmd, which impairs the catalytically necessary open‐to‐close transition, and by an exchange of a crucial histidine to a tyrosine. Mainly based on the presented data, a function of HmdII as Hmd isoenzyme, H2 sensor, FeGP‐cofactor storage protein and scaffold protein for FeGP‐cofactor biosynthesis could be excluded. Inspired by the recently found binding of HmdII to aminoacyl‐tRNA synthetases and tRNA, we tentatively consider HmdII as a regulatory protein for protein synthesis that senses the intracellular methylene‐H4MPT concentration.DatabaseStructural data are available in the Protein Data Bank under the accession numbers 4YT8; 4YT2; 4YT4 and 4YT5.
the transfer of a hydride ion fromH2 to methenyltetrahydromethanopterin (methenyl‐H4MPT+) to form methylene‐H4MPT. Its iron guanylylpyridinol (FeGP) cofactor plays a key role in H2 activation. Evidence is presented for O2 sensitivity of [Fe]‐hydrogenase under turnover conditions in the presence of reducing substrates, methylene‐H4MPT or methenyl‐H4MPT+/H2. Only then, H2O2 is generated, which decomposes
单铁加氢酶([Fe]-加氢酶)可逆地催化氢离子从H 2转移至亚甲基四氢甲蝶呤(methenyl-H 4 MPT +),形成亚甲基-H 4 MPT。其胍基铁吡啶铁(FeGP)辅因子在H 2活化中起关键作用。提出了在存在还原性底物,亚甲基-H 4 MPT或亚甲基-H 4 MPT + / H 2的情况下,在周转条件下[Fe]-加氢酶的O 2敏感性的证据。只有这样,H 2 O 2产生,分解FeGP辅因子;如通过光谱分析和失活酶的晶体结构所证明的。O 2还原为H 2 O 2需要还原剂,它可以是[Fe]-加氢酶反应过程中短暂形成的催化中间体。最可能的候选物质是氢化铁。通过催化反应的理论研究已经预测了其存在。该发现支持预测,因为描述了氢化极性化合物的氢化钌配合物的相同类型的还原反应。
Biosynthesis of the Iron-Guanylylpyridinol Cofactor of [Fe]-Hydrogenase in Methanogenic Archaea as Elucidated by Stable-Isotope Labeling
[Fe]-hydrogenase catalyzes the reversible hydride transfer from H(2) to methenyltetrahydromethanoptherin, which is an intermediate in methane formation from H(2) and CO(2) in methanogenic archaea. The enzyme harbors a unique active site iron-guanylylpyridinol (FeGP) cofactor, in which a low-spin Fe(II) is coordinated by a pyridinol-N, an acyl group, two carbon monoxide, and the sulfur of the enzyme's
[Fe]‐hydrogenase (Hmd), an enzyme of the methanogenic energy metabolism, harbors an iron‐guanylylpyridinol (FeGP) cofactor used for H2 cleavage. The generated hydride is transferred to methenyl‐tetrahydromethanopterin (methenyl‐H4MPT+). Most hydrogenotrophic methanogens contain the hmd‐related genes hmdII and hmdIII. Their function is still elusive. We were able to reconstitute the HmdII holoenzyme of Methanocaldococcus jannaschii with recombinantly produced apoenzyme and the FeGP cofactor, which is a prerequisite for in vitro functional analysis. Infrared spectroscopic and X‐ray structural data clearly indicated binding of the FeGP cofactor. Methylene‐H4MPT binding was detectable in the significantly altered infrared spectra of the HmdII holoenzyme and in the HmdII apoenzyme–methylene‐H4MPT complex structure. The related binding mode of the FeGP cofactor and methenyl‐H4MPT+ compared with Hmd and their multiple contacts to the polypeptide highly suggest a biological role in HmdII. However, holo‐HmdII did not catalyze the Hmd reaction, not even in a single turnover process, as demonstrated by kinetic measurements. The found inactivity can be rationalized by an increased contact area between the C‐ and N‐terminal folding units in HmdII compared with in Hmd, which impairs the catalytically necessary open‐to‐close transition, and by an exchange of a crucial histidine to a tyrosine. Mainly based on the presented data, a function of HmdII as Hmd isoenzyme, H2 sensor, FeGP‐cofactor storage protein and scaffold protein for FeGP‐cofactor biosynthesis could be excluded. Inspired by the recently found binding of HmdII to aminoacyl‐tRNA synthetases and tRNA, we tentatively consider HmdII as a regulatory protein for protein synthesis that senses the intracellular methylene‐H4MPT concentration.DatabaseStructural data are available in the Protein Data Bank under the accession numbers 4YT8; 4YT2; 4YT4 and 4YT5.