COMPONENTS OF GLYCINE REDUCTASE FROM EUBACTERIUM-ACIDAMINOPHILUM - CLONING, SEQUENCING AND IDENTIFICATION OF THE GENES FOR THIOREDOXIN REDUCTASE, THIOREDOXIN AND SELENOPROTEIN P(A)

The genes encoding thioredoxin reductase (trxB), thioredoxin (trxA), protein P(A) of glycine reductase (grdA) and the first 23 amino acids of the large subunit of protein P(C) of glycine reductase (grdC) belonging to the reductive deamination systems present in Eubacterium acidaminophilum were cloned and sequenced. The proteins were products of closely linked genes with 314 codons (thioredoxin reductase), 110 codons (thioredoxin), and 158 codons (protein P(A)). The protein previously called 'atypically small lipoamide dehydrogenase' or 'electron transferring flavoprotein' could now conclusively be identified as a thioredoxin reductase (subunit mass of 34781 Da) by the alignment with the enzyme of Escherichia coli showing the same typical order of the corresponding domains. The thioredoxin (molecular mass of 11 742 Da) deviated considerably from the known consensus sequence, even in the most strongly conserved redox-active segment WCGPC that was now GCVPC. The selenocysteine of protein P(A) (molecular mass of 16609 Da) was encoded by TGA. The protein was highly similar to those of Clostridium purinolyticum and Clostridium sticklandii involved in glycine reductase. Thioredoxin reductase and thioredoxin of E. acidaminophilum could be successfully expressed in E. coli.