Max-Planck-Institut fur terrestrische Mikrobiologie, Karl-von-Frisch-Strase, D-35043 Marburg, and Laboratorium fur Mikrobiologie, Fachbereich Biologie, Philipps-Universitat, Karl-von-Frisch-Strase, D-35032 Marburg, Germany
In 1933, Stephenson & Stickland (1933a) published that they had isolated from river mud, by the single cell technique, a methanogenic organism capable of growth in an inorganic medium with formate as the sole carbon source.

Biochemistry of methanogenesis: a tribute to Marjory Stephenson:1998 Marjory Stephenson Prize Lecture

How coenzyme B12 radicals are generated: the crystal structure of methylmalonyl-coenzyme A mutase at 2 A resolution.

Large amounts (estimates range from 70 Tg per year to 300 Tg per year) of the potent greenhouse gas methane are oxidized to carbon dioxide in marine sediments by communities of methanotrophic archaea and sulphate-reducing bacteria, and thus are prevented from escaping into the atmosphere. Indirect evidence indicates that the anaerobic oxidation of methane might proceed as the reverse of archaeal methanogenesis from carbon dioxide with the nickel-containing methyl-coenzyme M reductase (MCR) as the methane-activating enzyme. However, experiments showing that MCR can catalyse the endergonic back reaction have been lacking. Here we report that purified MCR from Methanothermobacter marburgensis converts methane into methyl-coenzyme M under equilibrium conditions with apparent V(max) (maximum rate) and K(m) (Michaelis constant) values consistent with the observed in vivo kinetics of the anaerobic oxidation of methane with sulphate. This result supports the hypothesis of 'reverse methanogenesis' and is paramount to understanding the still-unknown mechanism of the last step of methanogenesis. The ability of MCR to cleave the particularly strong C-H bond of methane without the involvement of highly reactive oxygen-derived intermediates is directly relevant to catalytic C-H activation, currently an area of great interest in chemistry.

The key nickel enzyme of methanogenesis catalyses the anaerobic oxidation of methane

Glutamate mutase from Clostridium cochlearium: the structure of a coenzyme B12-dependent enzyme provides new mechanistic insights.

Nickel homeostasis and nickel regulation: an overview.

Experiments are described to elucidate the structure and solvation of aquocobalamin (vitamin Biza, 1+) in the crystal and in aqueous solution. Aquocobalamin (1+) is the B12 derivative in which a water molecule replaces the axially coordinating organic substituent (methyl or 5'-desoxyadenosyl) at the P-side of the cobalt of the B12 coenzymes. (1) A single-crystal structure analysis of aquocobalamin perchlorate (l'ClO,), using synchrotron radiation in combination with an imaging plate detector, yielded the most accurate structural data ever determined for a B12 molecule. l'C10, crystallizes in the orthorhombic space group P212121, a = 15.042(11) A, b = 23.715(14) A, c = 25.104(12) A, with four 1'CIOi moieties plus about 100 solvent water molecules per unit cell; 22 867 independent and 20 942 significant intensity data were recorded to a nominal resolution of 0.8 A, and refinement against quantities led to a conventional R-value of 0.050 for all 22 867 observations and to a structural model with an average ESD for all carbon-carbon bonds of 0.003 A. In the crystal, the aquocobalamin ion has a very short axial bond between cobalt and the dimethylbenzimidazole (DMB) base of 1.925 (0.002) A, which is rationalized as resulting from the very weak trans axial donor (water). Steric repulsion between the DMB base and the corrin ring induced by this short Co-DMB bond leads to a relatively large "butteffly" deformation with an "upward" fold angle of 18.7 l(0.07)". The relevance of this observation for the "upward conformational deformation" hypothesis for the initiation of Co-C bond homolysis in coenzyme B12 dependent enzymes is discussed. (2) EXAFS spectra were taken from an authentic sample of the aquocobalamin perchlorate crystals used for the X-ray structure analysis, as well as from 1+C104 dissolved in a 1:l mixture of watedethylene glycol. Absorption spectra were recorded at 20 K between 7300 and 8700 eV, and the k3-weighted EXAFS was extracted for a k-value between 2.7 and 14.4 A-l. EXAFS spectra for solid and dissolved l'C10, agree closely, establishing identical cobalt coordination for the aquocobalamin ion in solution and in the solid state. A curve-fitting analysis on the Fourier filtered first-shell data yields a coordination number of 6 and an average distance of 1.90 A for both samples. There is no evidence for a longer Co-N distance. This refutes data published by Sagi and Chance (J. Am. Chem. Soc. 1992, 114, 8061). (3) NMR experiments are described, constituting the first detailed NMR investigations on a Bl2 derivative in H20, including 2D homo- and heteronuclear studies on aquocobalamin chloride (l+Cl-) and assignment of signals due to the exchangeable amide protons of all nitrogens as well a measurements of amide proton exchange rates. The NMR data confirm the occupation of the axial coordination site at the Co(II1) center by water, as well as the occurrence in solution of an intramolecular hydrogen bond to the axially coordinating water molecule, as observed in the crystal structure of l'C10,. However, significant differences of the structure of 1+ in crystals of l'C10, and of 1+ in aqueous solution are indicated from NOE data concerning the time-averaged conformation of the hydrogen-bonding c-acetamide side chain.

https://mcl1.ncifcrf.gov/dauter_pubs/115.pdf

Accurate Structural Data Demystify B-12 - High-Resolution Solid-State Structure of Aquocobalamin Perchlorate and Structure-Analysis of the Aquocobalamin Ion in Solution

The structure of a derivative of coenzyme F430 from methanogenic bacteria, the bromide salt of 12,13-diepi-F430 pentamethyl ester (5, X = Br), was determined by X-ray structure analysis. It reveals a more pronounced saddle-shaped out-of-plane deformation of the macrocycle than any hydroporphinoid Ni complex investigated so far. The crystal structure confirms the constitution proposed for coenzyme F430 (2) and shows that in the epimer 5, the three stereogenic centers in ring D, C(17), C(18), and C(19), have the (17S)-, (18S)-, and (19R)-configuration, respectively. Deuteration and 2D-NMR studies independently demonstrate that native coenzyme F430 (2) has the same configuration in ring D as the epimer 5. Therefore, our original tentative assignment of configuration at C(19) and C(18) [1] has to be reversed. This completes the assignment of configuration for all stereogenic centers in coenzyme F430, which has the structure shown in Formula2.

Coenzyme F430 from Methanogenic Bacteria: Complete Assignment of Configuration Based on an X‐Ray Analysis of 12,13‐Diepi‐F430 Pentamethyl Ester and on NMR Spectroscopy

Synthesis and reactions of tetrazolo[1,5‐α]pyrimidines

Unequivocal evidence for restricted rotation about a metal-arene bond caused by the steric effects of proximal ethyl groups; Crystal structure of dicarbonyltriphenylphosphine-(η6-1,3,5-triethyl-2,4,6-tris(trimethylsilylmethyl)benzene)molybdenum(0)

Gerald Färber

Papers

Accurate Structural Data Demystify B-12 - High-Resolution Solid-State Structure of Aquocobalamin Perchlorate and Structure-Analysis of the Aquocobalamin Ion in Solution

Coenzyme F430 from Methanogenic Bacteria: Complete Assignment of Configuration Based on an X‐Ray Analysis of 12,13‐Diepi‐F430 Pentamethyl Ester and on NMR Spectroscopy

Synthesis and reactions of tetrazolo[1,5‐α]pyrimidines

Unequivocal evidence for restricted rotation about a metal-arene bond caused by the steric effects of proximal ethyl groups; Crystal structure of dicarbonyltriphenylphosphine-(η6-1,3,5-triethyl-2,4,6-tris(trimethylsilylmethyl)benzene)molybdenum(0)