An elongated form of T4 glutaredoxin with four extra residues.

Two different forms of T4 glutaredoxin (thioredoxin) arising from the same gene on a multicopy plasmid in an Escherichia coli expression system have been isolated and characterized. Up to one-fourth of purified T4 glutaredoxin has an extension of four amino acids in the carboxy terminus, with the sequence aspartate, arginine, isoleucine, lysine. This four-residue extension may be caused by a translational +1 frameshift at the UGA terminator codon.