Format

Send to

Choose Destination
Biochemistry. 2004 Oct 5;43(39):12606-13.

Sugar binding induced charge translocation in the melibiose permease from Escherichia coli.

Author information

1
Max-Planck-Institut für Biophysik, Marie-Curie Strasse 15, 60439 Frankfurt/M, Germany.

Abstract

Electrogenic events associated with the activity of the melibiose permease (MelB), a transporter from Escherichia coli, were investigated. Proteoliposomes containing purified MelB were adsorbed to a solid supported lipid membrane, activated by a substrate concentration jump, and transient currents were measured. When the transporter was preincubated with Na(+) at saturating concentrations, a charge translocation in the protein upon melibiose binding could still be observed. This result demonstrates that binding of the uncharged substrate melibiose triggers a charge displacement in the protein. Further analysis showed that the charge displacement is neither related to extra Na(+) binding to the transporter, nor to the displacement of already bound Na(+) within the transporter. The electrogenic melibiose binding process is explained by a conformational change with concomitant displacement of charged amino acid side chains and/or a reorientation of helix dipoles. A kinetic model is suggested, in which Na(+) and melibiose binding are distinct electrogenic processes associated with approximately the same charge displacement. These binding reactions are fast in the presence of the respective cosubstrate (k > 50 s(-1)).

PMID:
15449950
DOI:
10.1021/bi0489053
[Indexed for MEDLINE]

Supplemental Content

Full text links

Icon for American Chemical Society
Loading ...
Support Center