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Nutrient Transport - Advanced Exercise 1

LamB facilitates diffusion of maltose and similar sugars across the outer membrane.

  1. The Transcription Units diagram on the “Transporter:phage lambda receptor protein” page shows lamB is part of an operon with malK and malM. What does malK encode? Why do you think LamB is synthesized together with MalK and MalM? Describe the scenario in which these proteins work together in maltose transport.
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  3. Schrimer et al. (1995) made a crystallographic evaluation of LamB in complex with maltose. What type of amino acids in LamB were found in that study to be necessary to compose the channel?
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  5. Now find these residues within the Sequence Features diagram for the LamB sequence itself--remember that they need to be labeled as important for sugar transport. List all of them.
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  7. If you deleted the gene encoding LamB from E. coli, would drug resistance be impacted? If so, how? Hint: Look at related reference abstracts. How could you counter this phenotype genetically without complementing the mutant strain with the lamB gene?
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  9. Use the Gene-Reaction Schematic to name another protein that can bring maltose from the external environment to the periplasmic space.
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  11. Although not much is known about the function of MalM, the Summary Section states it has a signal peptide.  Why would this protein need a signal peptide?