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Eur J Biochem. 1994 Jul 15;223(2):339-44.

Expression, purification and functional properties of a soluble form of Bradyrhizobium japonicum TlpA, a thioredoxin-like protein.

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1
Mikrobiologisches Institut, Eidgenössische Technische Hochschule, Zürich, Switzerland.

Abstract

The TlpA protein of Bradyrhizobium japonicum was previously identified genetically as a membrane-anchored, periplasmic thioredoxin-like protein. Here we describe the heterologous expression in Escherichia coli, subsequent purification and biochemical characterization of TlpA. A soluble form of TlpA, which lacks its N-terminal membrane anchor, was overexpressed in E. coli and purified by a two-step procedure. Pure TlpA was shown to be a monomer in solution and was active in reducing the disulfides of insulin and in reactivating reduced, denatured RNaseA. Evidence is presented that two non-active-site cysteine residues form an intramolecular disulfide bond, a feature that is not normally found in other prokaryotic thioredoxins.

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