Article
- The EMBO Journal (2002) 21, 3960 - 3969
- doi:10.1093/emboj/cdf405
Subject Categories:
Evolutionary domain fusion expanded the substrate specificity of the transmembrane electron transporter DsbD
Federico Katzen1, Meenal Deshmukh2, Fevzi Daldal2 and Jon Beckwith1
- Department of Microbiology and Molecular Genetics, Harvard Medical School, 200 Longwood Avenue, Boston, MA 02115 USA
- Department of Biology, Plant Science Institute, University of Pennsylvania, Philadelphia, PA 19104, USA
Correspondence to:
Jon Beckwith, E-mail: jbeckwith@hms.harvard.edu
Received 26 February 2002; Accepted 11 June 2002; Revised 3 June 2002
Abstract
Modular organization of proteins has been postulated as a widely used strategy for protein evolution. The multidomain transmembrane protein DsbD catalyzes the transfer of electrons from the cytoplasm to the periplasm of Escherichia coli. Most bacterial species do not have DsbD, but instead their genomes encode a much smaller protein, CcdA, which resembles the central hydrophobic domain of DsbD. We used reciprocal heterologous complementation assays between E.coli and Rhodobacter capsulatus to show that, despite their differences in size and structure, DsbD and CcdA are functional homologs. While DsbD transfers reducing potential to periplasmic protein disulfide bond isomerases and to the cytochrome c thioreduction pathway, CcdA appears to be involved only in cytochrome c biogenesis. Our findings strongly suggest that, by the acquisition of additional thiol-redox active domains, DsbD expanded its substrate specificity.
Keywords:
- CcdA,
- disulfide bond,
- DsbD,
- protein evolution,
- transmembrane electron transporter
