GalP (protein)

GalP is an integral membrane protein present in Escherichia Coli (1, 2). It is a Galactose-H+ symporter, of approximately 52Kda (3). Present on the inner membrane of the gram-negative E. Coli, GalP displays sequence homology to the GLUT1 transporters in mammals (4). This is shown in their similar substrate specificity and their sensitivity to the antibiotic forskolin (4). Owing to amino acid hydrophobic profiles, GalP, like GLUT1, is believed to have 12 transmembrane alpha helices (5). Both GalP and GLUT1 also have their N-terminus and C-terminus in the cytosol (6). For these reasons, study of GalP is thought to be indicative of the workings of the human-expressed GLUT1 sugar transporter (7). A member of the Major Facilitator Superfamily (MFS), GalP pumps only D-galactose into the cytosol against a concentration gradient by secondary active transport into the cell, using the electrochemical H+ gradient (7, 8). E. Coli will metabolise internalised galactose to glucose; which is obviously used to satisfy cellular energy requirements.