Related Experiment Video
Updated: May 5, 2026

Evaluation of Amino Acid Consumption in Cultured Bone Cells and Isolated Bone Shafts
Published on: April 13, 2022
Transport of basic amino acids in Riccia fluitans: Evidence for a second binding site
1Botanisches Institut I der Justus Liebig Universität, Senckenbergstr. 17-21, D-6300, Giessen, Federal Republic of Germany.
Abstract:
The transport of several amino acids with different side-chain characteristics has been investigated in the aquatic liverwort Riccia fluitans. i) The saturation of system I (neutral amino acids) by addition of excess α-aminoisobutyric acid to the external medium completely eliminated the electrical effects which are usually set off by neutral amino acids. Under these conditions arginine and lysine significantly depolarized the plasmalemma. ii) L- and D-lysine/arginine were discriminated against in favour of the L-isomers. iii) Increasing the external proton concentration in the interval pH 9 to 4.5 stimulated plasmalemma depolarization, electrical net current, and uptake of [(14)C]-basic amino acids. iv) Uptake of [(14)C]-glutamic acid took place only at acidic pHs. v) [(14)C]-histidine uptake had an optimum between pH 6 and 5.5. vi) Overlapping of the transport of basic, neutral, and acidic amino acids was common. It is suggested that besides system I, a second system (II), specific for basic amino acids, exists in the plasmalemma of Riccia fluitans. It is concluded that the amino-acid molecule with an uncharged side chain is the substrate for system I, which also binds and transports the neutral species of acidic amino acids, whereas system II is specific for amino acids with a positively charged side chain. The possibility of system II being a proton cotransport is discussed.
Related Concept Videos
Ligand Binding and Linkage
Allosteric Proteins-ATCase
Aspartate transcarbamoylase (ATCase) is a cytosolic enzyme that catalyzes the condensation of L-aspartate and carbamoyl phosphate to N-carbamoyl-L-aspartate. This reaction is the first step in pyrimidine biosynthesis. UTP and CTP, the end products of the pyrimidine synthesis...
Secondary Active Transport
Ligand Binding Sites
Protein-ligand interactions are quite specific; even though numerous potential ligands surround a cellular protein at any given time, only a particular ligand can bind to that protein. Moreover, a ligand binds only to a dedicated area on the surface of the protein, known as the...
Conserved Binding Sites
Binding sites are often located in large pockets, and if their location on a protein’s surface is unknown, it can be predicted using various approaches. The energetic method computationally...
Directing Proteins to the Rough Endoplasmic Reticulum

