Cannon, Kurt S.Or, EranClemons, William M.Shibata, YokoRapoport, Tom A.2019-10-142005Cannon, Kurt S., Eran Or, William M. Clemons, Yoko Shibata, and Tom A. Rapoport. 2005. “Disulfide Bridge Formation between SecY and a Translocating Polypeptide Localizes the Translocation Pore to the Center of SecY.” The Journal of Cell Biology 169 (2): 219–25. doi:10.1083/jcb.200412019.0021-95251540-8140http://nrs.harvard.edu/urn-3:HUL.InstRepos:41543072During their biosynthesis, many proteins pass through the membrane via a hydrophilic channel formed by the heterotrimeric Sec61/SecY complex. Whether this channel forms at the interface of multiple copies of Sec61/SecY or is intrinsic to a monomeric complex, as suggested by the recently solved X-ray structure of the Methanococcus jannaschii SecY complex, is a matter of contention. By introducing a single cysteine at various positions in Escherichia coli SecY and testing its ability to form a disulfide bond with a single cysteine in a translocating chain, we provide evidence that translocating polypeptides pass through the center of the SecY complex. The strongest cross-links were observed with residues that would form a constriction in an hourglass-shaped pore. This suggests that the channel makes only limited contact with a translocating polypeptide, thus minimizing the energy required for translocation.en-USJournal Article2019-10-1410.1083/jcb.200412019