@article{ReschkeSigfridssonKaufmannetal.2013,
  author    = {Reschke, Stefan and Sigfridsson, Kajsa G. V. and Kaufmann, Paul and Leidel, Nils and Horn, Sebastian and Gast, Klaus and Schulzke, Carola and Haumann, Michael and Leimk{\"u}hler, Silke},
  title     = {Identification of a bis-molybdopterin intermediate in molybdenum cofactor biosynthesis in escherichia coli},
  series = {The journal of biological chemistry},
  volume    = {288},
  journal   = {The journal of biological chemistry},
  number    = {41},
  publisher = {American Society for Biochemistry and Molecular Biology},
  address   = {Bethesda},
  issn      = {0021-9258},
  doi       = {10.1074/jbc.M113.497453},
  pages     = {29736 -- 29745},
  year      = {2013},
  abstract  = {The molybdenum cofactor is an important cofactor, and its biosynthesis is essential for many organisms, including humans. Its basic form comprises a single molybdopterin (MPT) unit, which binds a molybdenum ion bearing three oxygen ligands via a dithiolene function, thus forming Mo-MPT. In bacteria, this form is modified to form the bis-MPT guanine dinucleotide cofactor with two MPT units coordinated at one molybdenum atom, which additionally contains GMPs bound to the terminal phosphate group of the MPTs (bis-MGD). The MobA protein catalyzes the nucleotide addition to MPT, but the mechanism of the biosynthesis of the bis-MGD cofactor has remained enigmatic. We have established an in vitro system for studying bis-MGD assembly using purified compounds. Quantification of the MPT/molybdenum and molybdenum/phosphorus ratios, time-dependent assays for MPT and MGD detection, and determination of the numbers and lengths of Mo-S and Mo-O bonds by X-ray absorption spectroscopy enabled identification of a novel bis-Mo-MPT intermediate on MobA prior to nucleotide attachment. The addition of Mg-GTP to MobA loaded with bis-Mo-MPT resulted in formation and release of the final bis-MGD product. This cofactor was fully functional and reconstituted the catalytic activity of apo-TMAO reductase (TorA). We propose a reaction sequence for bis-MGD formation, which involves 1) the formation of bis-Mo-MPT, 2) the addition of two GMP units to form bis-MGD on MobA, and 3) the release and transfer of the mature cofactor to the target protein TorA, in a reaction that is supported by the specific chaperone TorD, resulting in an active molybdoenzyme.},
  language  = {en}
}
@article{FabianGastLaueetal.2013,
  author    = {Fabian, Heinz and Gast, Klaus and Laue, Michael and Jetzschmann, Katharina J. and Naumann, Dieter and Ziegler, Andreas and Uchanska-Ziegler, Barbara},
  title     = {IR spectroscopic analyses of amyloid fibril formation of beta(2)-microglobulin using a simplified procedure for its in vitro generation at neutral pH},
  series = {Biophysical chemistry : an international journal devoted to the physical chemistry of biological phenomena},
  volume    = {179},
  journal   = {Biophysical chemistry : an international journal devoted to the physical chemistry of biological phenomena},
  number    = {5},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {0301-4622},
  doi       = {10.1016/j.bpc.2013.05.001},
  pages     = {35 -- 46},
  year      = {2013},
  abstract  = {beta(2)-microglobulin (beta(2)m) is known to be the major component of fibrillar deposits in the joints of patients suffering from dialysis-related amyloidosis. We have developed a simplified procedure to convert monomeric recombinant beta(2)m into amyloid fibrils at physiological pH by a combination of stirring and heating, enabling us to follow conformational changes associated with the assembly by infrared spectroscopy and electron microscopy. Our studies reveal that fibrillogenesis begins with the formation of relatively large aggregates, with secondary structure not significantly altered by the stirring-induced association. In contrast, the conversion of the amorphous aggregates into amyloid fibrils is associated with a profound re-organization at the level of the secondary and tertiary structures, leading to non-native like parallel arrangements of the beta-strands in the fully formed amyloid structure of beta(2)m. This study highlights the power of an approach to investigate the formation of beta(2)m fibrils by a combination of biophysical techniques including IR spectroscopy.},
  language  = {en}
}