A mathematical model for membrane transport of amino acid and Na+ in vesicles |
| |
Authors: | Anita K Babcock Thomas Q Garvey III Mones Berman |
| |
Institution: | (1) Laboratory of Theoretical Biology, National Cancer Institute, 20014 Bethesda, Maryland;(2) Digestive Diseases Branch, National Institute of Arthritis, Metabolism, and Digestive Diseases, Building 10, Room 4B-56, 20014 Bethesda, Maryland |
| |
Abstract: | Summary A model with a carrier having sites for both amino acid and Na+ can account for AIB ( -aminoisobutyric acid) transport kinetics observed in membrane vesicles from SV3T3 (simian virus 40-tranformed Balb/c3T3 cells) and 3T3 (the parent cell line). The main feature of this cotransport model is that Na+ binding to carrier decreases the effectiveK
m for AIB transport, Na+ transport kinetics observed in both vesicle systems can be described by passive (possibly facilitated) diffusion. The lag of Na+ transport across the membrane compared to that for AIB, coupled to the Na+-dependent decrease in theK
m
for AIB, accounts for the overshoot in intravesicular AIB observed for SV3T3 in the presence of an initial Na+ gradient. Extra-vesicular Na+ maintains a derease in theK
m
for AIB influx before intra-vesicular Na+ has accumulated to balance it with a comparable decrease in theK
m
for AIB efflux. 3T3 vesicles display little overshoot, and this finding can be explained mostly by a lower carrier affinity for Na+. |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|