Lactose permease of Escherichia coli: properties of mutants defective in substrate translocation
| Autor: | Robert Seckler, Peter Overath, Jean-Marc Neuhaus, Isolde Riede, H Bocklage, Jörg Soppa, U. Weigel, J K Wright, G Aichele, Benno Müller-Hill |
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| Rok vydání: | 1987 |
| Předmět: |
DNA
Bacterial Lactose permease animal structures Monosaccharide Transport Proteins Mutant Biology medicine.disease_cause Translocation Genetic Escherichia coli medicine Amino Acid Sequence chemistry.chemical_classification Multidisciplinary Symporters integumentary system Permease Membrane transport protein Escherichia coli Proteins Wild type Membrane Transport Proteins Biological Transport Galactosides Membrane transport Amino acid Kinetics Biochemistry chemistry Mutation biology.protein Research Article |
| Zdroj: | Proceedings of the National Academy of Sciences. 84:5535-5539 |
| ISSN: | 1091-6490 0027-8424 |
| DOI: | 10.1073/pnas.84.16.5535 |
| Popis: | 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. |
| Databáze: | OpenAIRE |
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