Osmosensor and osmoregulator properties of the betaine carrier BetP from Corynebacterium glutamicum in proteoliposomes

Autor(en): Rubenhagen, R
Ronsch, H
Jung, H
Kramer, R
Morbach, S
Stichwörter: Biochemistry & Molecular Biology; CELL-WALL; COMPATIBLE SOLUTES; ESCHERICHIA-COLI; GLYCINE BETAINE; LOCAL-ANESTHETIC TETRACAINE; PHYSIOLOGY; POLYACRYLAMIDE GELS; PROTEINS; STRESS; UPTAKE SYSTEM
Erscheinungsdatum: 2000
Herausgeber: AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
Journal: JOURNAL OF BIOLOGICAL CHEMISTRY
Volumen: 275
Ausgabe: 2
Startseite: 735
Seitenende: 741
Zusammenfassung: 
The secondary glycine betaine uptake system BetP of Corynebacterium glutamicum was purified from Escherichia coli membranes in strep-tagged form after heterologous expression of the betP gene and was reconstituted in E, coli lipids. BetP retained its kinetic properties (V-max and K-m for betaine and Na+) as compared with intact cells. The influence of driving forces (Na+ gradient and/or electrical potential) on betaine uptake was quantified in proteoliposomes. BetP was effectively regulated by the external osmolality and was stimulated by the local anesthetic tetracaine. A shift of the optimum of osmotic stimulation to higher osmolalities was linearly correlated with an increasing share of phosphatidyl glycerol, the major lipid of the C. glutamicum plasma membrane in the E. coli lipid proteoliposomes, This finding correlates with results demonstrating an identical shift when betP was expressed in E. coli instead of C. glutamicum. These data indicate that (i) BetP comprises all elements of osmosensing and osmoregulatory mechanisms of betaine uptake, (ii) osmoregulation of BetP is directly related to protein/membrane interactions, (iii) the turgor pressure presumably plays no major role in osmoregulation of BetP, and (iv) the regulatory properties of BetP may be related to the physical state of the surrounding membrane.
ISSN: 00219258
DOI: 10.1074/jbc.275.2.735

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