Opening the periplasmic cavity in lactose permease is the limiting step for sugar binding
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چکیده
منابع مشابه
Opening the periplasmic cavity in lactose permease is the limiting step for sugar binding.
The lactose permease (LacY) catalyzes galactoside/H(+) symport via an alternating access mechanism in which sugar- and H(+)-binding sites in the middle of the molecule are alternatively exposed to either side of the membrane by opening and closing of inward- and outward-facing cavities. The crystal structures of wild-type LacY, as well as accessibility data for the protein in the membrane, prov...
متن کاملOpening and closing of the periplasmic gate in lactose permease.
X-ray crystal structures of lactose permease (LacY) reveal pseudosymmetrically arranged N- and C-terminal six-transmembrane helix bundles surrounding a deep internal cavity open on the cytoplasmic side and completely closed on the periplasmic side. The residues essential for sugar recognition and H(+) translocation are located at the apex of the cavity and are inaccessible from the outside. On ...
متن کاملSugar binding and protein conformational changes in lactose permease.
Lactose permease is an integral membrane protein that uses the cell membrane's proton gradient for import of lactose. Based on extensive biochemical data and a substrate-bound crystal structure, intermediates involved in lactose/H(+) co-transport have been suggested. Yet, the transport mechanism, especially the coupling of protonation states of essential residues and protein conformational chan...
متن کاملLactose permease and the alternating access mechanism.
Crystal structures of the lactose permease of Escherichia coli (LacY) reveal 12, mostly irregular transmembrane α-helices surrounding a large cavity open to the cytoplasm and a tightly sealed periplasmic side (inward-facing conformation) with the sugar-binding site at the apex of the cavity and inaccessible from the periplasm. However, LacY is highly dynamic, and binding of a galactopyranoside ...
متن کاملSugar recognition by the lactose permease of Escherichia coli.
Biochemical, luminescence and mass spectroscopy approaches indicate that Trp-151 (helix V) plays an important role in hydrophobic stacking with the galactopyranosyl ring of substrate and that Glu-269 (helix VIII) is essential for substrate affinity and specificity. The x-ray structure of the lactose permease (LacY) with bound substrate is consistent with these conclusions and suggests that a po...
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ژورنال
عنوان ژورنال: Proceedings of the National Academy of Sciences
سال: 2011
ISSN: 0027-8424,1091-6490
DOI: 10.1073/pnas.1112157108