ISSN:
1432-2048
Schlagwort(e):
Amino acid uptake
;
Pod wall
;
Proton
;
Threonine cotransport
;
Vicia (threonine uptake)
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Biologie
Notizen:
Abstract Kjeldahl assays showed that the pod wall of Vicia faba fruits behaves as a transitory reservoir of nitrogen. We have studied the properties and energetics of amino-acid uptake during the accumulating stage of pod wall development. A comparative analysis using various inhibitors or activators of the proton pump has been carried out i) on threonine uptake, ii) on the acidifying activity of the tissues, and iii) on the transmembrane potential difference of mesocarp cells. Except for the effect of dicyclohexylcarbodiimide which could not be satisfactorily explained, all other results obtained with ATPase inhibitors, uncouplers and fusicoccin were consistent with the view of a transport energized by the proton-motive force. Adding threonine to a medium containing fragments of pericarp or of endocarp induced a pH change (to-wards more alkaline values) of the medium and a membrane depolarization of the storage cells which depended on the amino-acid concentration added. These data indicate H+-threonine cotransport in the pod wall of broad bean. Moreover, because p-chloromercuribenzenesulphonic acid inhibits threonine uptake without affecting the transmembrane potential difference, it is concluded that the threonine carrier possesses a functional SH-group located at the external side of the plasmalemma.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/BF00395479
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