SecY Complex
Protein-Conducting
Channel

Transmembrane protein
responsible for transporting
polypeptides across cell membranes
in prokaryotes.

Subunits

Original Settings

Select α subunit
Forms the pore through which proteins pass

Select β subunit
Not necessary for channel function

Select γ subunit
Holds α subunit in proper conformation

Residue Properties

Cartoon View

Hydrophobic Residues
Hydrophobic (blue) band around portion of
protein inserted in membrane.

Polar Residues
Polar (yellow) residues surround channel
openings.

Electrostatic Surface
Exposed regions have charge, while region
within membrane has little charge.

Channel Function

Original Settings

Cartoon View

Pore Ring (White)
Narrowest point of channel. Isoleucine,
valine, and leucine residues.

Pore Plug (Green)
Closes the channel to polypeptides and small
molecules. Upon binding of the signal
sequence of a polypeptide, the pore plug
moves and provides access through the pore
ring.

A Closer Look

Overall View of the Pore and Plug


Citation: van den Berg, B. Clemons Jr., W.M. Collinson, I. Modis, Y. Hartmann, E. Harrison, S.C. Rapoport, T.A. X-ray structure of a protein-conducting channel. Nature v427 pp.36-44 , 2004