ISBN: 978-83-60043-10-3 - eurobic9

Eurobic9, 2-6 September, 2008, Wrocław, Poland
SL31. Investigating the Post-translational Modification of Cysteine
Dioxygenase
T. Kleffmann a , S. M. Wilbanks a , G. N. L. Jameson b
a Department of Biochemistry, University of Otago, PO Box 56, Dunedin, New Zealand.
b Department of Chemistry, University of Otago, PO Box 56, Dunedin, New Zealand
e-mail: gjameson@chemistry.otago.ac.nz
It is crucial for healthy cells that the correct concentrations of the amino acid cysteine are maintained. A build up
of cysteine is observed in Parkinson’s disease [1, 2] and other pathologies when there is a failure to break
cysteine down. Degradation of cysteine involves a sequence of enzymatic reactions. The first and regulating
reaction is catalysed by the enzyme cysteine dioxygenase (CDO).
Present in organisms from bacteria [3] to humans [4], CDO catalyses the oxidation of cysteine to a cysteine
sulfinate (Scheme). The oxidation occurs by addition of molecular oxygen (O2) to the sulfur atom of the cysteine
thiol (-SH). The heart of the active site of CDO is a mono-iron site coordinated by three histidine residues. CDO
is therefore a member of a larger group of proteins known as the non-heme mono-iron proteins, which have
gained considerable interest in recent years and have been the subject of numerous reviews. This interest stems
from their ability, even with such a simple active site, to catalyze a wide range of processes that contribute to a
variety of important biochemical processes.
CDO’s catalytic site is also unusual in containing a cross-link (Cys93 to Tyr157) observed in only three other
enzymes. [5-7] Formation of this cross-link converts this enzyme from an immature, less active form to the
mature, fully active form. The cross-link formation in CDO depends on the substrate cysteine, [8] suggesting a
novel feedback mechanism for enzyme activation in control of sulfur metabolism. We have isolated immature
protein and completely determined the cross-link’s structure by mass spectrometry. Although the available X-ray
crystal structures show “snap shots” of the catalytic site, mechanisms both of cross-link formation and cysteine
oxidation remain to be determined.
In this presentation we will bring the present knowledge up-to-date and sketch the way in which our future
studies will go.
Acknowledgement: The Chemistry Department and the Division of Sciences of the University of Otago, and the
University of Otago Research Grant Committee for financial support.
References:
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(1-2), 216 (1990).
[3] J. E. Dominy Jr., C. R. Simmons, P. A. Karplus, A. M. Gehring, M. H. Stipanuk, J. Bacteriol., 188 (15), 5561
(2206).
[4] S. Ye, X. A. Wu, L. Wei, D. Tang, P. Sun, M. Bartlam, Z. Rao, J. Biol. Chem., 282 (5), 3391 (2007).
[5] N. Ito, S. E. V. Phillips, C. Stevens, Z. B. Ogel, M. J. McPherson, J. N. Keen, K. D. S. Yadav, P. F. Knowles,
Nature, 350 (6313), 87 (1991).
[6] R. Schnell, T. Sandalova, U. Hellman, Y. Lindqvist, G. Schneider, J. Biol. Chem., 280 (29), 27319 (2005).
[7] M. M. Whittaker, J. W. Whittaker, J. Biol. Chem., 278 (24), 22090 (2003).
[8] J. E. Dominy Jr., J. Hwang, S. Guo, L. L. Hirschberger, S. Zhang, M. H. Stipanuk, J. Biol. Chem., 283 (18),
12188 (2008).
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