Glycerol facilitator GlpF and the associated aquaporin family of channels.
The aqua (glycero) porins conduct water (and glycerol) across cell membranes. The structure of these channels reveals a tripathic channel that supports a hydrophobic surface and, opposite to this, a line of eight hydrogen-bond acceptors and four hydrogen-bond donors. The eight carbonyls act as acceptors for water (or glycerol OH) molecules. The central water molecule in the channel is oriented to polarize hydrogen atoms outward from the center. This arrangement suggests how the structure prevents the potentially lethal conduction of protons across the membrane. The structure also suggests the mechanism behind the selectivity of aquaglyceroporins for glycerol, the basis for enantioselectivity among alditols, and the basis for the prevention of any leakage of the electrochemical gradient.
Stroud
Robert M
RM
Department of Biochemistry & Biophysics, School of Medicine, 600 16th Street, University of California San Francisco, CA 94143-2240, USA. stroud@msg.ucsf.edu
Miercke
Larry J W
LJ
O'Connell
Joseph
J
Khademi
Shahram
S
Lee
John K
JK
Remis
Jonathan
J
Harries
William
W
Robles
Yaneth
Y
Akhavan
David
D
D020346:Aquaporins / Q000737:chemistry / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism*; D005990:Glycerol / Q000378:metabolism*; D007477:Ions / Q000378:metabolism; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011522:Protons; D014867:Water / Q000378:metabolism
D020346:Aquaporins; D029968:Escherichia coli Proteins; D007477:Ions; D011522:Protons; D014867:Water; C078043:GlpF protein, E coli; D005990:Glycerol