Influence of the oxidoreductase ER57 on the folding of an antibody fab fragment.

Oxidation and folding of secretory proteins in the endoplasmic reticulum (ER) depends on the presence of chaperones and oxidoreductases. Two of the oxidoreductases present in the ER of mammalian cells are protein disulfide isomerase (PDI) and ERp57. In this study, we investigated the influence of ERp57 on the in vitro reoxidation and refolding of an antibody Fab fragment.

Refolding of inclusion body proteins.

Genome sequencing projects have led to the identification of an enormous number of open reading frames that code for unknown proteins. Elucidation of the structure and function of these proteins makes it necessary to produce proteins fast, in high yields and at low cost. The recombinant expression of proteins in bacterial hosts often results in the formation of inclusion bodies.

Modulation of the ATPase cycle of BiP by peptides and proteins.

BiP, the Hsp70 homologue of the endoplasmic reticulum, interacts with its non-native substrate proteins in an ATP-dependent manner. This interaction is coupled to the ATPase cycle of the chaperone. Binding of short, synthetic peptides stimulate the ATPase activity of BiP.

Folding and oxidation of the antibody domain C(H)3.

The non-covalent homodimer formed by the C-terminal domains of the IgG1 heavy chains (C(H)3) is the simplest naturally occurring model system for studying immunoglobulin folding and assembly. In the native state, the intrachain disulfide bridge, which connects a three-stranded and a four-stranded beta-sheet is buried in the hydrophobic core of the protein. Here, we show that the disulfide bridge is not required for folding and association, since the reduced C(H)3 domain folds to a dimer with defined secondary and tertiary structure.

Interaction of the chaperone BiP with an antibody domain: implications for the chaperone cycle.

BiP is an Hsp70 homologue found in the endoplasmic reticulum of eukaryotic cells. Like other Hsp70 chaperones, BiP interacts with its substrate proteins in an ATP-dependent manner. The functional analysis has so far been performed mainly with short, synthetic peptides.