4ubg

Publication Abstract from PubMed

Cysteine dioxygenase (CDO) is a non-heme mono-iron enzyme with an unusual posttranslational modification in close proximity to the ferrous iron active site. This modification, a cysteine to tyrosine thioether bond, crosslinks two beta-strands of the beta-barrel. We have investigated its role in catalysis through a combined crystallographic and kinetic approach. The C93G variant lacks the crosslink and shows little structural change from wild-type suggesting that the crosslink does not stabilize an otherwise unfavorable conformation. A pH dependent kinetic study shows that both crosslinked and uncrosslinked CDO are active but the pH optimum decreases with the presence of the crosslink. This result reflects the effect of the thioether bond on the pKa of Y157 and this residue's role in catalysis. At higher pH, kcat is also higher for the crosslinked form extending the pH range of activity. We therefore propose that the crosslink also increases activity by controlling deleterious interactions involving the thiol/ate of C93.

The Cys-Tyr Crosslink of Cysteine Dioxygenase changes the Optimum pH of Reaction without Structural Change.,Davies CG, Fellner M, Tchesnokov EP, Wilbanks SM, Jameson GN Biochemistry. 2014 Nov 12. PMID:25390690^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.