Temperature effects on the kinetic properties of the rabbit intestinal oligopeptide cotransporter PepT1.
The effects of temperature on the functional properties of the intestinal oligopeptide transporter PepT1 from rabbit have been investigated using electrophysiological methods. The dipeptide Gly-Gln at pH 6.5 or 7.5 was used as substrate. Raising the temperature in the range 20-30 °C causes an increase in the maximal transport-associated current (I (max)) with a Q (10) close to 4. Higher temperatures accelerate the rate of decline of the presteady-state currents observed in the absence of organic substrate. The voltage dependencies of the intramembrane charge movement and of the time constant of decline are both shifted towards more negative potentials by higher temperatures. The shift is due to a stronger action of temperature on the outward rate of charge movement compared to the inward rate, indicating a lower activation energy for the latter process. Consistently, the activation energy for the complete cycle is similar to that of the inward rate of charge movement. Temperature also affects the binding rate of the substrate: the K (0.5) -V curve is shifted to more negative potentials by higher temperatures, resulting in a lower apparent affinity in the physiological range of potentials. The overall efficiency of transport, estimated as the I (max)/K (0.5) ratio is significantly increased at body temperature.
Laboratory of Cellular and Molecular Physiology, Department of Biotechnology and Life Sciences, University of Insubria, Via Dunant 3, 21100, Varese, Italy.
Elena
E
Bossi
Francesca
F
Cherubino
Eleonora
E
Margheritis
Ayodele Stephen
AS
Oyadeyi
Alessandra
A
Vollero
Antonio
A
Peres
D000818:Animals; D001492:Bass; D007700:Kinetics; D009865:Oocytes; D018408:Patch-Clamp Techniques; D000074011:Peptide Transporter 1; D011817:Rabbits; D013045:Species Specificity; D027981:Symporters / Q000378:metabolism*; D013696:Temperature; D014982:Xenopus laevis
D000074011:Peptide Transporter 1; D027981:Symporters