Format

Send to

Choose Destination
Biochemistry. 2011 Mar 15;50(10):1634-40. doi: 10.1021/bi101988s. Epub 2011 Feb 8.

Site-directed alkylation studies with LacY provide evidence for the alternating access model of transport.

Author information

1
Department of Physiology, University of California, Los Angeles, California 90095, United States.

Abstract

In total, 59 single Cys-replacement mutants in helix VII and helix X of the lactose permease of Escherichia coli were subjected to site-directed fluorescence labeling in right-side-out membrane vesicles to complete the testing of Cys accessibility or reactivity. For both helices, accessibility/reactivity is relatively low at the level of the sugar-binding site where the helices are tightly packed. However, labeling of Cys substitutions in helix VII with tetramethylrhodamine-5-maleimide decreases from the middle toward the cytoplasmic end and increases toward the periplasmic end. Helix X is labeled mainly on the side facing the central hydrophilic cavity with relatively small or no changes in the presence of ligand. In contrast, sugar binding causes a significant increase in accessibility/reactivity at the periplasmic end of helix VII. When considered with similar findings from N-ethylmaleimide alkylation studies, the results confirm and extend support for the alternating access model.

PMID:
21254783
PMCID:
PMC3057939
DOI:
10.1021/bi101988s
[Indexed for MEDLINE]
Free PMC Article

Publication types, MeSH terms, Substances, Grant support

Publication types

MeSH terms

Substances

Grant support

Supplemental Content

Full text links

Icon for American Chemical Society Icon for PubMed Central
Loading ...
Support Center