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Structure and Mechanism of the Lactose Permease of

Summary: Structure and Mechanism of the
Lactose Permease of
Escherichia coli
Jeff Abramson,1
Irina Smirnova,3
Vladimir Kasho,3
Gillian Verner,3
H. Ronald Kaback,3
* So Iwata1,2
Membrane transport proteins that transduce free energy stored in electro-
chemical ion gradients into a concentration gradient are a major class of
membrane proteins. We report the crystal structure at 3.5 angstroms of the
Escherichia coli lactose permease, an intensively studied member of the major
facilitator superfamily of transporters. The molecule is composed of N- and
C-terminal domains, each with six transmembrane helices, symmetrically po-
sitioned within the permease. A large internal hydrophilic cavity open to the
cytoplasmic side represents the inward-facing conformation of the transporter.
The structure with a bound lactose homolog, -D-galactopyranosyl-1-thio- -
D-galactopyranoside, reveals the sugar-binding site in the cavity, and residues


Source: Akabas, Myles - Department of Physiology and Biophysics, Albert Einstein College of Medicine, Yeshiva University


Collections: Biology and Medicine