| Summary: | Members of the Major Facilitator Superfamily (MFS) make up the largest family of secondary active transporters, they mediate a diverse set of functions by controlling the movement of ions and small molecules across cell membranes. Members of the MFS share a set of common structural motifs consisting of transmembrane ɑ-helical segments. The glycerol-3-phosphate transporter (GlpT), is an example of an MFS transporter with 12 α-helices ordered into two domains. Recent study on MFS transporter LacY, has implied an increased stability localized to the vicinity of the first helices of the protein. If this observation is found in other MFS proteins it could suggest a folding principle for other MFS transporters, whereby the first helix of the protein is acting as a stable unit that supports the process of folding. The inherent magnified stability of the helix 1 may also aid in other cellular events, where transporters or receptors are integrated into the membrane by anchoring to the membrane as well as becoming part of the unit that first penetrates the membrane leaflet. This work is focused on the stability analysis via alanine substitutions along the first alpha helix of the first domain of GlpT, compared to similar and corresponding mutations along the first helix of its second domain. The transporters stability is estimated by unfolding assays coupled with the decrease of secondary structure as measured by circular dichroism spectroscopy. Additional methods such as fluorescence spectroscopy, temperature denaturation and ligand binding assays have also been used in order to gain deeper understanding of the nature of the GlpT unfolding and its helical stability.
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