منابع مشابه
Residues gating the periplasmic pathway of LacY.
X-ray crystal structures of LacY (lactose permease of Escherichia coli) exhibit a large cytoplasmic cavity containing the residues involved in sugar binding and H(+) translocation at the apex and a tightly packed side facing the periplasm. However, biochemical and biophysical evidence provide a strong indication that a hydrophilic pathway opens on the external surface of LacY with closing of th...
متن کاملThe Cys154-->Gly mutation in LacY causes constitutive opening of the hydrophilic periplasmic pathway.
The lactose permease of Escherichia coli (LacY) is a highly dynamic membrane transport protein, while the Cys154-->Gly mutant is crippled conformationally. The mutant binds sugar with high affinity, but catalyzes very little translocation across the membrane. In order to further investigate the defect in the mutant, fluorescent maleimides were used to examine the accessibility/reactivity of sin...
متن کاملRole of Conserved Gly-Gly Pairs on the Periplasmic Side of LacY.
On the periplasmic side of LacY, two conserved Gly-Gly pairs in helices II and XI (Gly46 and Gly370, respectively) and helices V and VIII (Gly159 and Gly262, respectively) allow close packing of each helix pair in the outward (periplasmic)-closed conformation. Previous studies demonstrate that replacing one Gly residue in each Gly-Gly pair with Trp leads to opening of the periplasmic cavity wit...
متن کاملCrystal structure of a LacY-nanobody complex in a periplasmic-open conformation.
The lactose permease of Escherichia coli (LacY), a dynamic polytopic membrane protein, catalyzes galactoside-H+ symport and operates by an alternating access mechanism that exhibits multiple conformations, the distribution of which is altered by sugar binding. We have developed single-domain camelid nanobodies (Nbs) against a mutant in an outward (periplasmic)-open conformation to stabilize thi...
متن کاملGalactoside-Binding Site in LacY
Although an X-ray crystal structure of lactose permease (LacY) has been presented with bound galactopyranoside, neither the sugar nor the residues ligating the sugar can be identified with precision at ~3.5 Å. Therefore, additional evidence is important for identifying side chains likely to be involved in binding. On the basis of a clue from site-directed alkylation suggesting that Asn272, Gly2...
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ژورنال
عنوان ژورنال: Biochemistry
سال: 2009
ISSN: 0006-2960,1520-4995
DOI: 10.1021/bi801976r