Abstract
Integral outer membrane receptors for iron chelates and vitamin B12 carry out specific ligand transport against a concentration gradient. Energy for active transport is obtained from the proton-motive force of the inner membrane through physical interaction with TonB-ExbB-ExbD, an inner membrane complex. Here we report the crystal structure of an active transport, outer membrane receptor at 2.4 Å resolution. Two distinct functional domains are revealed: (i) a 22-stranded β-barrel that spans the outer membrane and contains large extracellular loops which appear to function in ligand binding; and (ii) a globular N-terminal domain that folds into the barrel pore, inhibiting access to the periplasm and contributing two additional loops for potential ligand binding. These loops could provide a signaling pathway between the processes of ligand recognition and TonB-mediated transport. The blockage of the pore suggests that the N-terminal domain must undergo a conformational rearrangement to allow ligand transport into the periplasm.
Original language | English (US) |
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Pages (from-to) | 56-63 |
Number of pages | 8 |
Journal | Nature Structural Biology |
Volume | 6 |
Issue number | 1 |
DOIs | |
State | Published - 1999 |
ASJC Scopus subject areas
- Structural Biology
- Biochemistry
- Genetics