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Updated: Jan 25, 2026

Analysis of Protein Folding, Transport, and Degradation in Living Cells by Radioactive Pulse Chase
Published on: February 12, 2019
Two cysteines in each periplasmic domain of the membrane protein DsbB are required for its function in protein
G Jander1, N L Martin, J Beckwith
1Department of Microbiology, Harvard Medical School, Boston, MA 02115.
Abstract:
DsbB is a protein component of the pathway that leads to disulfide bond formation in periplasmic proteins of Escherichia coli. Previous studies have led to the hypothesis that DsbB oxidizes the periplasmic protein DsbA, which in turn oxidizes the cysteines in other periplasmic proteins to make disulfide bonds. Gene fusion approaches were used to show that (i) DsbB is a membrane protein which spans the membrane four times and (ii) both the N- and C-termini of the protein are in the cytoplasm. Mutational analysis shows that of the six cysteines in DsbB, four are necessary for proper DsbB function in vivo. Each of the periplasmic domains of the protein has two essential cysteines. The two cysteines in the first periplasmic domain are in a Cys-X-Y-Cys configuration that is characteristic of the active site of other proteins involved in disulfide bond formation, including DsbA and protein disulfide isomerase.
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