Lactose permease of Escherichia coli: properties of mutants defective in substrate translocation.
AUTOR(ES)
Overath, P
RESUMO
Mutants of lactose permease of Escherichia coli with amino acid changes (Gly-24----Glu; Gly-24----Arg; Pro-28---Ser; Gly-24, Pro-28----Glu-Ser and Gly-24, Pro-28----Arg-Ser) within a putative membrane-spanning alpha-helix (Phe-Gly-Leu-Phe-Phe-Phe-Phe-Tyr-Phe-Phe-Ile-Met-Gly- Ala-Tyr-Phe-Pro-Phe-Phe-Pro-Ile) are incorporated into the cytoplasmic membrane. The mutant proteins retain the ability to bind galactosides, and the affinity for several substrates is actually increased. However, the rate of active transport is decreased to 0.01% of the wild-type rate in the mutants carrying Arg-24 or Arg-24, Ser-28. Kinetic analysis demonstrates that the two mutants require 10 min to cause occupied binding sites for galactoside and H+ to change their exposure from the periplasm to the cytoplasm as compared to 50 ms in the wild type. The effect is less pronounced when these sites are unoccupied.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=298897Documentos Relacionados
- The substrate-binding site in the lactose permease of Escherichia coli
- Functional complementation of internal deletion mutants in the lactose permease of Escherichia coli.
- Conformational flexibility at the substrate binding site in the lactose permease of Escherichia coli
- Properties of permease dimer, a fusion protein containing two lactose permease molecules from Escherichia coli.
- Properties and purification of an active biotinylated lactose permease from Escherichia coli.
