The betaine transporter BetP: lessons from X-ray and electron crystallography combined with biochemistry
The betaine uptake carrier BetP from the soil bacterium Corynebacterium glutamicum is a secondary active, sodium coupled transporter of the BCCT transporter family. Beside its catalytic activity (betaine transport) it has both sensory and regulatory functions in perception of and response to hyperosmotic stress. Both its two and three-dimensional structure was recently solved by electron (Ziegler et al., 2004) and X-ray crystallography (Ressl et al., 2009). Its activity state depends on several factors, including the integrity of its C-terminal domain, the concentration of internal potassium ions, the surface charge of the surrounding membrane, as well as mutual interactions with other parts of the carrier protein (Rübenhagen et al., 2001, Ott et al., 2008). A combination of (i) functional data obtained from scanning mutagenesis of the regulatory, C-terminal domain of BetP together with interaction studies, of (ii) data obtained from EPR spectroscopy upon site-directed spin labeling, and (iii) structural data from both 2D and 3D crystal structures led to novel insight in the functional properties of this active solute transporter.
vCal
iCal