Participation of Low Molecular Weight Electron Carriers in Oxidative Protein Folding

Oxidative protein folding is mediated by a proteinaceous electron relay system, in which the concerted action of protein disulfide isomerase and Ero1 delivers the electrons from thiol groups to the final acceptor. Oxygen appears to be the final oxidant in aerobic living organisms, although the existence of alternative electron acceptors, e.g. fumarate or nitrate, cannot be excluded. Whilst the protein components of the system are well-known, less attention has been turned to the role of low molecular weight electron carriers in the process. The function of ascorbate, tocopherol and vitamin K has been raised recently. In vitro and in vivo evidence suggests that these redox-active compounds can contribute to the functioning of oxidative folding. This review focuses on the participation of small molecular weight redox compounds in oxidative protein folding

Antioxidant efficacy and adhesion rescue by a recombinant mussel foot protein-6

Mytilus foot protein type 6 (mfp-6) is crucial for maintaining the reducing conditions needed for optimal wet adhesion in marine mussels. In this report we describe the expression and production of a recombinant Mytilus californianus foot protein type 6 variant 1 (rmfp-6.1) fused with a hexa-histidine affinity tag in Escherichia coli and its purification by affinity chromatography. Recombinant mfp-6 showed high purification yields of 5–6 mg/L cell culture and excellent solubility in low pH buffers that retard oxidation of its many thiol groups. Purified rmfp-6.1 protein showed high DPPH radical scavenging activity as compared to Vitamin C. Using the highly sensitive surface force apparatus (SFA) technique to measure interfacial surface forces in the nanoNewton range we show that rmfp-6.1 is also able to rescue the oxidation-dependent adhesion loss of mussel foot protein 3 (mfp-3) at pH 3. The adhesion rescue is related to a reduction of dopaquinone back to DOPA in mfp-3 which is the reverse reaction observed during the detrimental enzymatic browning process in fruits and vegetables. Broadly viewed, rmfp-6.1 has potential as a versatile antioxidant for applications ranging from personal products to anti-spoilants for perishable foods during processing and storage