Low-affinity, high-capacity system of glucose transport in the ruminal bacterium Streptococcus bovis: evidence for a mechanism of facilitated diffusion.
The glucose phosphotransferase system (PTS) of Streptococcus bovis could not account for the glucose consumption of exponential cultures, and the kinetics of glucose transport were biphasic. A PTS-deficient mutant lost the high-affinity, low-capacity system but retained its ability to take up glucose at high substrate concentrations. The low-affinity, high-capacity system did not require a proton motive force or ATP and could not be driven by an artificial membrane potential in the presence or absence of sodium. Since low-affinity transport was directly proportional to the external substrate concentration and exhibited counterflow kinetics, it appeared that a facilitated-diffusion mechanism was responsible for glucose transport at high substrate concentrations.
Russell
J B
JB
Agricultural Research Service, Cornell University, Ithaca, New York 14853.
D000818:Animals; D001693:Biological Transport, Active; D004058:Diffusion; D005947:Glucose / Q000378:metabolism*; D007700:Kinetics; D012417:Rumen / Q000382:microbiology; D013291:Streptococcus / Q000378:metabolism*
D005947:Glucose