Sensor modules of the osmoregulatory glycine betaine uptake carrier from Corynebacterium glutamicum: structure and interaction with the transport domain Transport-Domäne

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The tightly coupled betaine uptake system BetP of Corynebacterium glutamicum converts the energy of an electrochemical Na+ gradient into an extremely high chemical gradient of betaine. The activity of BetP strictly depends on the presence of an osmotic gradient across the plasma membrane. BetP was shown to be both osmosensor and transporter. The transporter is a membrane protein with 12 transmembrane segments and includes prominent N- and C-terminal extensions facing the cytoplasm, a property observed in many pro- and eukarytic osmoactive membrane proteins. These extensions have been shown to be involved in the sensor function. The N- and C-terminal modules will be separately expressed in different lengths, as well as the membrane-embedded part of BetP. We propose to study the structure of the hydrophilic modules of BetP and its structural interaction with the transport domain by using various spectroscopic techniques, in particular NMR spectroscopy, and also X-ray crystallography.