Analysis of Escherichia coli TonB membrane topology by use of PhoA fusions. |
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| Authors: | S K Roof J D Allard K P Bertrand and K Postle |
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| Affiliation: | Department of Microbiology, Washington State University, Pullman 99164-4233. |
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| Abstract: | Alkaline phosphatase (PhoA) fusions to TonB amino acids 32, 60, 125, 207, and 239 (the carboxy terminus) all showed high PhoA activity; a PhoA fusion to TonB amino acid 12 was inactive. The full-length TonB-PhoA fusion protein was associated with the cytoplasmic membrane and retained partial TonB function. These results support a model in which TonB is anchored in the cytoplasmic membrane by its hydrophobic amino terminus, with the remainder of the protein, including its hydrophobic carboxy terminus, extending into the periplasm. |
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