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Structural determination of wild-type lactose permease
Authors:
L.
Guan
(University of California, USA)
,
O.
Mirza
(University of Copenhagen, Denmark)
,
G.
Verner
(University of California, USA.)
,
S.
Iwata
(Diamond Light Source)
,
H. R.
Kaback
(Imperial College London, U.K.)
Co-authored by industrial partner:
No
Type:
Journal Paper
Journal:
Proceedings Of The National Academy Of Sciences
, VOL 104 (39)
, PAGES 15294 - 15298
State:
Published (Approved)
Published:
September 2007
Abstract: Here we describe an x-ray structure of wild-type lactose permease (LacY) from Escherichia coli determined by manipulating phospholipid content during crystallization. The structure exhibits the same global fold as the previous x-ray structures of a mutant that binds sugar but cannot catalyze translocation across the membrane. LacY is organized into two six-helix bundles with twofold pseudosymmetry separated by a large interior hydrophilic cavity open only to the cytoplasmic side and containing the side chains important for sugar and H+ binding. To initiate transport, binding of sugar and/or an H+ electrochemical gradient increases the probability of opening on the periplasmic side. Because the inward-facing conformation represents the lowest free-energy state, the rate-limiting step for transport may be the conformational change leading to the outward-facing conformation.
Journal Keywords: Conformation ; Mechanism ; Membrane Protein ; Transport ; X-Ray Structure
Subject Areas:
Biology and Bio-materials
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