Relation of chemotactic response to the amount of receptor: evidence for different efficiencies of signal transduction.
We determined the content of galactose-glucose-, maltose-, and ribose-binding proteins in cells of Escherichia coli K-12 grown in a variety of media and also measured the respective transport and chemotactic activities that depend on those binding proteins. Correlation of the level of induction of a particular binding protein with the extent of tactic activity mediated by that protein indicates that the magnitude of the tactic response to a particular stimulating compound is a direct function of the number of receptors per cell. In contrast, comparison of the magnitudes of response to substances recognized by independent receptors indicates that some stimulus-receptor complexes are more effective in eliciting tactic responses than are others. Thus, the magnitude of response to any particular stimulating compound is a function both of the number of receptors per cell and of the effectiveness of the stimulus-receptor complex. Considerations of available information about the tactic response to maltose suggest that the effectiveness of a stimulus-receptor complex is related to the transducer with which the receptor interacts. The tar product appears to be a relatively effective transducer of the signals it accepts from receptors for aspartate, alpha-methylaspartate, and maltose, whereas the trg product appears to be a relatively ineffective transducer of signals it accepts from receptors for galactose and ribose.
D001426:Bacterial Proteins / Q000032:analysis* / Q000378:metabolism; D002633:Chemotaxis; D004926:Escherichia coli / Q000032:analysis / Q000502:physiology*; D005690:Galactose / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D008320:Maltose / Q000378:metabolism; D009997:Osmotic Pressure; D011955:Receptors, Drug / Q000032:analysis* / Q000378:metabolism; D012266:Ribose / Q000378:metabolism
D001426:Bacterial Proteins; D011955:Receptors, Drug; D012266:Ribose; D008320:Maltose; D005947:Glucose; D005690:Galactose