ISSN:
1432-1424
Keywords:
amine
;
porter
;
Chara australis
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Summary The rate of transport of amine ions intoChara australis internodes is studied by measuring changes in membrane current when amine solutions are presented to voltage-clamped cells. The dependence of this rate on ion concentration is investigated for a series of alkyl-amine ions: methyl-, ethyl-, isopropyl-, dimethyl-, trimethyl- and tetramethylammonium. A Michaelis-Menten relationship is displayed by all except tri- and tetramethylammonium, where currents are irregular and difficult to reproduce. Evidence suggests that the different ions cross the plasmalemma via a common uniport.K M values for this porter increase as the amine ion becomes more highly substituted. TheV m values are similar for all amines and lie within the range 10 to 100 mA m−2 (for cell potential at −200 mV). The changes inK M indicate that hydrogen bonding may be involved in the binding interaction.V m varies with external pH in a way which suggests that an ionizable group on the transport protein with pKa≈5.8 directly affects the transport rate.K M is independent of external pH over the range 4.5 to 10.5
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01872130
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