Towards the molecular mechanism of Na+/solute symport in prokaryotes

Autor(en): Jung, H
Stichwörter: Biochemistry & Molecular Biology; Biophysics; COMPLETE GENOME SEQUENCE; ESCHERICHIA-COLI; LACTOSE PERMEASE; MEMBRANE TOPOLOGY; NA+/PROLINE TRANSPORTER; PERMEASE GENE PUTP; PROLINE TRANSPORT-SYSTEM; PSEUDOMONAS-PUTIDA-U; SALMONELLA-TYPHIMURIUM; secondary transport; sodium/proline transporter PutP; sodium/solute symport; STAPHYLOCOCCUS-AUREUS
Erscheinungsdatum: 2001
Herausgeber: ELSEVIER
Journal: BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS
Volumen: 1505
Ausgabe: 1, SI
Startseite: 131
Seitenende: 143
Zusammenfassung: 
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. (C) 2001 Elsevier Science B.V. All rights reserved.
ISSN: 00052728
DOI: 10.1016/S0005-2728(00)00283-8

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