Mass-spectrometric characterization of two posttranslational modifications of cysteine dioxygenase

Abstract

Recent crystal structures of cysteine dioxygenase (CDO) suggest the presence of two posttranslational modifications adjacent to the catalytic iron center: a thioether cross-link between Cys93 and Tyr157 and extra electron density at Cys164 which was variously explained as cystine or cysteine sulfinic acid. Purification of recombinant rat CDO yields "mature" and "immature" forms with distinct electrophoretic mobilities. We have positively identified and characterized the two modifications in the products of three sequential proteolytic digestions using liquid chromatography coupled with tandem mass spectrometry. The cross-link is unique to the mature form and was identified in an ion of m/z 3..