PMID:11248195
| Citation |
Jung, H (2001) Towards the molecular mechanism of Na(+)/solute symport in prokaryotes. Biochim. Biophys. Acta 1505:131-43 |
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| Abstract |
The Na(+)/solute symporter family (SSF, TC No. 2.A.21) contains more than 40 members of pro- and eukaryotic origin. Besides their sequence similarity, the transporters share the capability to utilize the free energy stored in electrochemical Na(+) gradients for the accumulation of solutes. As part of catabolic pathways most of the transporters are most probably involved in the acquisition of nutrients. Some transporters play a role in osmoadaptation. With a high resolution structure still missing, a combination of genetic, protein chemical and spectroscopic methods has been used to gain new insights into the structure and molecular mechanism of action of the transport proteins. The studies suggest a common 13-helix motif for all members of the SSF according to which the N-terminus is located in the periplasm and the C-terminus is directed into the cytoplasm (except for proteins containing a N- or C-terminal extension). Furthermore, an amino acid substitution analysis of the Na(+)/proline transporter (PutP) of Escherichia coli, a member of the SSF, has identified regions of particular functional importance. For example, amino acids of TM II of PutP proved to be critical for high affinity binding of Na(+) and proline. In addition, it was shown that ligand binding induces widespread conformational alterations in the transport protein. Taken together, the studies substantiate the common idea that Na(+)/solute symport is the result of a series of ligand-induced structural changes. |
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| Keywords |
Amino Acid Sequence; Amino Acid Transport Systems, Neutral; Bacterial Proteins/metabolism; Binding Sites; Carrier Proteins/chemistry; Carrier Proteins/genetics; Carrier Proteins/metabolism; Cations, Monovalent; Cytoplasm/metabolism; Escherichia coli/metabolism; Escherichia coli Proteins; Ligands; Models, Chemical; Molecular Sequence Data; Periplasm/metabolism; Proline/metabolism; Protein Conformation; Sodium/metabolism; Symporters |
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