Dynamics and Function of Spin Labelled ABC Transport System Studied by Multi-Frequency EPR

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The current transport model of ABC transporters is essentially based on the biochemical, biophysical and structural investigations of the maltose transporter MalFGK2 of E. coli/Salmonella. Due to some unique features of this system it is questionable whether this transport model holds for all ABC transporters. Here, the histidine ABC transporter from Salmonella typhimurium, HisJ/LAO-HisQMP2, and of the ECF (“energy-coupling factor”) transporter family, the biotin transporter BioMNY are regarded as complementary model systems for ABC transporters. Based on our recent results we will focus now on the interaction between the substrate binding protein HisJ and HisQMP2 and on substrate and nucleotide induced conformational changes of ECF transporters. The functionally related conformational changes of site-directed spin labeled variants of these transporters will be followed during the transport cycle by multi-frequency cw and pulse EPR spectroscopy with the aim to unravel the transport mechanism(s) on molecular level. In addition we intend to develop and apply new methodological approaches in the field of EPR spectroscopy including MD simulation based EPR spectra calculations.