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.

See also

• Transmembrane protein
• List of proteins

References

• Horne, P., and Henderson, P. J. (1983) The association of proton movement with galactose transport into subcellular membrane vesicles of Escherichia coli. Biochem J 210, 699-705.
• Cairns, M. T., McDonald, T. P., Horne, P., Henderson, P. J., and Baldwin, S. A. (1991) Cytochalasin B as a probe of protein structure and substrate recognition by the galactose/H+ transporter of Escherichia coli. J Biol Chem 266, 8176-83.
• Dill, K. A., and Shortle, D. (1991) Denatured states of proteins. Annu Rev Biochem 60, 795-825.
• Xu, Q., and Keiderling, T. A. (2004) Effect of sodium dodecyl sulfate on folding and thermal stability of acid-denatured cytochrome c: a spectroscopic approach. Protein Sci 13, 2949-59.
• Zhu, W., and Becker, D. F. (2005) Exploring the proline-dependent conformational change in the multifunctional PutA flavoprotein by tryptophan fluorescence spectroscopy. Biochemistry 44, 12297-306.
• Demchenko, A. P. (1986) Fluorescence analysis of protein dynamics. Essays Biochem 22, 120-57.
• Martin, G. E., Seamon, K. B., Brown, F. M., Shanahan, M. F., Roberts, P. E., and Henderson, P. J. (1994) Forskolin specifically inhibits the bacterial galactose-H+ transport protein, GalP. J Biol Chem 269, 24870-7.
• Macpherson, A. J., Jones-Mortimer, M. C., Horne, P., and Henderson, P. J. (1983) Identification of the GalP galactose transport protein of Escherichia coli. J Biol Chem 258, 4390-6.