Berlin 2005 – wissenschaftliches Programm
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AKB: Biologische Physik
AKB 200: Poster Session II
AKB 200.64: Poster
Dienstag, 8. März 2005, 17:00–19:00, Poster TU C
Multi-Frequency EPR studies on Quinoprotein Ethanol Dehydrogenase:Characterization of the novel PQQ cofactor — •Robert Bittl1, Christopher Kay1, Bina Mennenga2, and Helmut Görisch2 — 1Institut für Experimentalphysik, Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany — 2Fachgebiet Technische Biochemie, Institut für Biotechnologie, Technische Universität Berlin, 13353 Berlin, Germany
Pyrroloquinoline quinone (PQQ) is one of several quinone cofactors utilized in a class of dehydrogenases, known as quinoproteins. The quinoprotein methanol dehydrogenase (MDH) is among the best-characterised PQQ-dependent enzymes thus far. MDH has an α2β2 tetrameric structure with each β-subunit folded around the surface of an α-subunit. The PQQ cofactor is bound to a Ca2+ ion and sandwiched between a tryptophane residue and an unusual eight-membered disulfide ring structure formed from adjacent cysteine residues.
Here we describe the first detailed characterization of the enzyme-bound PQQ in both wild type and mutant proteins lacking the disulfide ring, using multi-frequency/resonance EPR methods. Thus, we have determined the principal values of the rhombic g-tensor [1], and from pulsed ENDOR experiments at X-Band and W-Band, supported by DFT calculations, we have determined and assigned many of the proton hyperfine couplings. From HYSCORE experiments, the hyperfine couplings from the two nitrogens in the cofactor could be determined.
[1] C. W. M. Kay, B. Mennenga, H. Görisch and R. Bittl, FEBS Lett 564 (2004) 69-72.