Open AccessValinomycin-induced cation transport in vesicles does not reflect the activity of K+ transport systems in Escherichia coli
Author(s) -
Karlheinz Altendorf,
Wolfgang Epstein,
Annett Lohmann
Publication year - 1986
Publication title -
journal of bacteriology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.652
H-Index - 246
eISSN - 1067-8832
pISSN - 0021-9193
DOI - 10.1128/jb.166.1.334-337.1986
Subject(s) - valinomycin , vesicle , escherichia coli , biology , membrane transport , biochemistry , vesicular transport protein , biophysics , mutant , nigericin , transport system , membrane transport protein , membrane potential , membrane , membrane protein , transport engineering , engineering , gene
Transport systems for K+ in Escherichia coli are not detectable in membrane vesicles, but vesicles will take up K+ (and Rb+) in the presence of valinomycin. It is generally believed that valinomycin acts as a lipid-soluble cation carrier and that it does not interact with or activate cation transport systems. This view is challenged by Bhattacharyya et al. (Proc. Natl. Acad. Sci. USA 68:1448-1492, 1971), who reported reduced uptake in vesicles from E. coli mutants with K+ transport defects. We reexamined this question with some of the same mutants and were unable to confirm a correlation of valinomycin-induced vesicle transport with transport properties in intact cells. We found great variability in transport activity of vesicles from these E. coli K-12 strains and believe such variability as well as possible contamination with intact cells accounts for the earlier report. Our data do not support the idea that valinomycin-mediated transport in vesicles is related to physiological K+ transport systems.