Physiological evidence for an interaction between Glu-325 and His-322 in the lactose carrier of Escherichia coli
| Autor: | T. Hastings Wilson, Manuel F. Varela, Jong-In Lee |
|---|---|
| Rok vydání: | 1996 |
| Předmět: |
Monosaccharide Transport Proteins
Molecular Sequence Data Mutant Biophysics Glutamic Acid Lactose medicine.disease_cause Biochemistry chemistry.chemical_compound Escherichia coli medicine Point Mutation Histidine Salt bridge Melibiose DNA Primers chemistry.chemical_classification Mutation Base Sequence Symporters Escherichia coli Proteins Mutagenesis Membrane Transport Proteins Biological Transport Gene Expression Regulation Bacterial Cell Biology Cation cotransport Amino acid Kinetics chemistry Lactose carrier Fermentation Mutagenesis Site-Directed Protons |
| Zdroj: | Biochimica et Biophysica Acta (BBA) - Biomembranes. 1278:111-118 |
| ISSN: | 0005-2736 |
| DOI: | 10.1016/0005-2736(95)00209-x |
| Popis: | Site-directed mutagenesis and second-site suppressor analysis have proven to be useful approaches to examine the role of charged amino acids in the structure and function of the lactose carrier of Escherichia coli . A lactose carrier mutant Glu-325 → Ser failed to ferment melibiose and showed white clones on melibiose MacConkey indicator plates. Several red revertants were isolated from these plates. Two of these revertants showed a double mutation, the original mutation (Glu-325 → Ser) plus His-322 → Asp. Seven revertants showed a second site mutation His-322 → Asn. Although the second site revertants failed to accumulate sugars they do show more rapid uptake of melibiose into cells containing α-galactosidase than the original mutant Glu-325 → Ser. The complete loss of transport activity due to the removal of the negative charge at 325 can be partially compensated for by the introduction of a new negative charge at 322. A site-directed double mutant His-322 → Asn/Glu-325 → Asn showed a greater rate of lactose uptake ( V max ) than either of the single mutants His-322 → Asn or Glu-325 → Asn. It was concluded that there is some type of physiological interaction (possibly a salt bridge) between His-322 and Glu-325. |
| Databáze: | OpenAIRE |
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