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bioRxiv · 10.1101/2020.05.31.125815

Alteration of Substrate-Induced Conformational Changes of Escherichia coli Melibiose Permease by Mutating Arg149

Lin, Y.
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Abstract

Fourier transform infrared difference spectroscopy and fluorescence spectroscopic techniques have been used to obtain information about substrate-induced structural changes of the melibiose permease mutant R149C, compared with the Cys-less, which were reconstituted into liposomes. ATR-FTIR evidences show that Na+-induced difference spectra of R149C and Cys-less are similar. However, Na+ induces some new peaks for R149C mutant permease. This means that replacement of Arg-149 by Cys may affect the structure of MelB, and then affect the binding of Na+. Melibiose-induced difference spectra of R149C in the presence of Na+ show some peaks in the amide I region not seen in Cys-less, corresponding to turns, {beta}-sheets, -helix changes. This suggests that R149C mutant permease undergo some different secondary structure changes compared to Cys-less mutant permease, when binding melibiose. Comparison of the permease intrinsic fluorescence variations of R149C and Cys-less indicate that there are similar substrate binding properties between R149C and Cys-less. When analyzing the effects of different sugars it appears that the R149C mutant is more sensitive to the sugar. All these data indicate that replacement of Arg-149 by Cys will affect Na+ and sugar binding, and enhance the selectivity and sensitivity to sugars.

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Lin, Y.. 2020-06-01. Alteration of Substrate-Induced Conformational Changes of Escherichia coli Melibiose Permease by Mutating Arg149. https://doi.org/10.1101/2020.05.31.125815

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