Substrate and Cofactor Range Differences of Two Cysteine Dioxygenases from Ralstonia eutropha H16

ABSTRACTCysteine dioxygenases (Cdos), which catalyze the sulfoxidation of cysteine to cysteine sulfinic acid (CSA), have been extensively studied in eukaryotes because of their roles in several diseases. In contrast, only a few prokaryotic enzymes of this type have been investigated. InRalstonia eutrophaH16, two Cdo homologues (CdoA and CdoB) have been identified previously.In vivostudies showed thatEscherichia colicells expressing CdoA could convert 3-mercaptopropionate (3MP) to 3-sulfinopropionate (3SP), whereas no 3SP could be detected in cells expressing CdoB. The objective of this study was to confirm these findings and to study both enzymes in detail by performing anin vitrocharacterization. The proteins were heterologously expressed and purified to apparent homogeneity by immobilized metal chelate affinity chromatography (IMAC). Subsequent analysis of the enzyme activities revealed striking differences with regard to their substrate ranges and their specificities for the transition metal cofactor, e.g., CdoA catalyzed the sulfoxidation of 3MP to a 3-fold-greater extent than the sulfoxidation of cysteine, whereas CdoB converted only cysteine. Moreover, the dependency of the activities of the Cdos fromR. eutrophaH16 on the metal cofactor in the active center could be demonstrated. The importance of CdoA for the metabolism of the sulfur compounds 3,3′-thiodipropionic acid (TDP) and 3,3′-dithiodipropionic acid (DTDP) by further converting their degradation product, 3MP, was confirmed. Since 3MP can also function as a precursor for polythioester (PTE) synthesis inR. eutrophaH16, deletion ofcdoAmight enable increased synthesis of PTEs.

Expression and Purification of His-chIFN-α and its Antiviral Activity Assay

In this paper, Chicken alpha interferon (IFN-α) gene was cloned into pUC19-His expression vector, then the recombinant expression vector was transformed into host bacteria E. coli BL21. The recombinant chicken IFN-α was induced to express by IPTG, then the protein expression was analyzed with SDS-PAGE. Under the condition that the recombinant protein was induced to express with 1 mM IPTG at 37 °C, the expressed protein was inclusion body. His-chIFN-α was purified by Ni-metal chelate affinity chromatography. His-chIFN-α was shown to inhibit the replication of Newcastle disease virus in CEF cells.