Ot. Mesmer et al., USE OF GLUCOSE-TRANSPORT MUTANTS TO EXAMINE THE INTRINSIC-PROPERTIES OF GLUCOSE-TRANSPORT PROCESSES IN RAT MYOBLASTS, Biochemistry and molecular biology international, 36(3), 1995, pp. 605-616
Glucose transport mutants were used to examine the intrinsic propertie
s of glucose transport processes in rat myoblasts. Studies with mutant
s devoid of any functional glucose transporter revealed that substanti
al amount of sugar analogues was internalized via simple diffusion; ho
wever, equilibration of these analogues across the plasma membrane was
not achieved after 1 min of incubation at 23 degrees C. The rates of
internalization were substantially higher with sugar analogues that we
re phosphorylated by intracellular kinases. Mutants harbouring only on
e functional GLUT transporter were also used to examine the intrinsic
properties of specific GLUT transporters. The preferred substrate for
the GLUT 1 transporter was 2-deoxy-D-glucose (dGlc); the transport aff
inity for this substrate was reduced by energy uncouplers. Studies wit
h mutants possessing only the GLUT 4 transporter revealed that this tr
ansporter existed in a high and a low affinity form. The former was re
sponsible for dGlc uptake; whereas the latter was for the uptake of bo
th 3-O-methyl-D-glucose (MeGlc) and dGlc; only the former was affected
by energy uncouplers. These studies illustrated the usefulness of mut
ants in characterizing glucose transport processes.