title: Lactococcus lactis TrxD represents a subgroup of thioredoxins prevalent in Gram-positive bacteria containing WCXDC active site motifs.
abstract: Three protein disulfide reductases of the thioredoxin superfamily from the industrially important Gram-positive Lactococcus lactis (LlTrxA, LlTrxD and LlNrdH) are compared to the "classical" thioredoxin from Escherichia coli (EcTrx1). LlTrxA resembles EcTrx1 with a WCGPC active site motif and other key residues conserved. By contrast, LlTrxD is more distantly related and contains a WCGDC motif. Bioinformatics analysis suggests that LlTrxD represents a subgroup of thioredoxins from Gram-positive bacteria. LlNrdH is a glutaredoxin-like electron donor for ribonucleotide reductase class Ib. Based on protein-protein equilibria LlTrxA (E°'=-259mV) and LlNrdH (E°'=-238mV) show approximately 10mV higher standard state redox potentials than the corresponding E. coli homologues, while E°' of LlTrxD is -243mV, more similar to glutaredoxin than "classical" thioredoxin. EcTrx1 and LlTrxA have high capacity to reduce insulin disulfides and their exposed active site thiol is alkylated at a similar rate at pH 7.0. LlTrxD on the other hand, is alkylated by iodoacetamide at almost 100 fold higher rate and shows no activity towards insulin disulfides. LlTrxA, LlTrxD and LlNrdH are all efficiently reduced by NADPH dependent thioredoxin reductase (TrxR) from L. lactis and good cross-reactivity towards E. coli TrxR was observed with LlTrxD as the notable exception.
authors.affiliation: Enzyme and Protein Chemistry, Department of Systems Biology, Søltofts Plads, Building 224, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark.
authors.forename: Olof
authors.initials: O
authors.lastname: Björnberg
authors.affiliation: Enzyme and Protein Chemistry, Department of Systems Biology, Søltofts Plads, Building 224, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark.
authors.forename: Petr
authors.initials: P
authors.lastname: Efler
authors.affiliation: Enzyme and Protein Chemistry, Department of Systems Biology, Søltofts Plads, Building 224, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark.
authors.forename: Epie Denis
authors.initials: ED
authors.lastname: Ebong
authors.affiliation: Enzyme and Protein Chemistry, Department of Systems Biology, Søltofts Plads, Building 224, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark.
authors.forename: Birte
authors.initials: B
authors.lastname: Svensson
authors.affiliation: Enzyme and Protein Chemistry, Department of Systems Biology, Søltofts Plads, Building 224, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark. Electronic address: ph@bio.dtu.dk.
authors.forename: Per
authors.initials: P
authors.lastname: Hägglund
mesh_terms: D020816:Amino Acid Motifs; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D020134:Catalytic Domain; D004926:Escherichia coli; D013294:Lactococcus lactis / Q000201:enzymology*; D009249:NADP; D010084:Oxidation-Reduction; D017386:Sequence Homology, Amino Acid; D013879:Thioredoxins / Q000737:chemistry* / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D013879:Thioredoxins; D009249:NADP
keywords: Disulfide reduction; Lactic acid bacteria; Redox potential; Thiol-disulfide exchange; Thioredoxin