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. 1999 Feb 2;96(3):939–944. doi: 10.1073/pnas.96.3.939

Figure 2.

Figure 2

Capillary assays with cells of strain YZ11 (23) expressing plasmid-encoded mutant forms of DC-MBP. This strain contains wild-type MBP at 23% of the induced level from a single chromosomal gene not containing a mutation affecting the pre-MBP leader peptide (15). The ordinate values represent the accumulations of cells in capillaries containing the concentrations of maltose indicated on the abscissa. These responses were normalized to the response of each strain to 1 mM l-aspartate. This concentration gives the peak accumulation to this alternative attractant sensed by Tar. The response of strain YZ11 containing the vector plasmid pBR322, and therefore no competing DC-MBP, was set to 100%, which corresponds to about 40,000 cells per capillary. Symbols: (•), vector plasmid; (○) DC-MBP; (▵), T53I DC-MBP; (□) D55N DC-MBP; (◊), R367A DC-MBP. The shift in the peak from 1 mM to 0.1 mM maltose with T53I and D55N DC-MBP presumably occurs because these proteins compete with wild-type MBP in maltose transport. Inhibition of maltose uptake increases periplasmic maltose concentrations and heightens sensitivity in maltose taxis (4).