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Stimulatory effect of lithium ion on proline transport by whole cells of Escherichia coli

Authors :
Kayama, Y
Kawasaki, T
Source :
Journal of Bacteriology; October 1976, Vol. 128 Issue: 1 p157-164, 8p
Publication Year :
1976

Abstract

The effect of monovalent cations on proline transport in whole cells of Escherichia coli K-12 has been examined. Lithium ion added to the uptake medium stimulated proline transport severalfold and K+ and Na+ were slightly effective, whereas Rb+, Cs+, and NH4+ were completely without effect. The stimulatory effect of Li+ on proline transport was not due to an increase in osmolarity of the uptake medium, and d 5 mM p-chloromercuribenzene sulfonic acid completely blocked this effect of Li+ without having any effect on the basal rate of proline transport. The Arrhenius plots for Li+-stimulated transport showed a clear transition point at 35 degrees C in addition to 20 degrees C which was also detectable in the basal transport. Lithium ion stimulated proline transport synergistically in the presence of glucose and succinate as a carbon source. The addition of 2.5 mM KCN or 0.5 mM arsenate did not inhibit this synergistic effect, although the presence of these inhibitors inhibited completely the stimulation of proline transport induced by the addition of carbon source. Carbonylcyanide m-chlorophenylhydrazone and 2,4-dinitrophenol blocked both the basal and Li+-stimulated proline transport. When membrane potential of E. coli cells was measured by the dibenzyldimethylammonium uptake method, the incubation of Li+ with the cells did not affect the preexisting membrane potential. These results suggest that Li+ stimulates proline transport by intact cells of E. coli in a manner somewhat affecting membrane component(s) different from the transport carrier of proline. It is uncertain whether the effect of Li+ is directly involved in the mechanisms of energy coupling of proline transport.

Details

Language :
English
ISSN :
00219193 and 10985530
Volume :
128
Issue :
1
Database :
Supplemental Index
Journal :
Journal of Bacteriology
Publication Type :
Periodical
Accession number :
ejs57598302
Full Text :
https://doi.org/10.1128/jb.128.1.157-164.1976