Encyclopedia of Biophysics

Living Edition
| Editors: Gordon Roberts, Anthony Watts, European Biophysical Societies

Na+/Melibiose Membrane Transport Protein, MelB

  • Lan GuanEmail author
Living reference work entry
DOI: https://doi.org/10.1007/978-3-642-35943-9_10082-1



Melibiose permease (MelB) is encoded by the melB gene in the melAB operon, which is present in many Gram-negative bacteria. MelB belongs to the glycoside–pentoside–hexuronide:cation symporter (GPH) family (TC 2.A.2) of the major facilitator superfamily (MFS). MelB catalyzes the transport of di- or trisaccharides containing a d-galactopyranosyl ring or galactose, and the native substrate is melibiose, a disaccharide formed by an α-1,6 linkage between galactose and glucose ( d-Gal-α(1 → 6)- d-Glc) (Fig. 1). It can be also formed by invertase-mediated hydrolysis of raffinose, which produces one melibiose and one fructose.
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  1. Bassilana M, Pourcher T, Leblanc G (1987) Facilitated diffusion properties of melibiose permease in Escherichia coli membrane vesicles. Release of co-substrates is rate limiting for permease cycling. J Biol Chem 262, 16865–16870.Google Scholar
  2. Ethayathulla AS, Yousef MS, Amin A, Leblanc G, Kaback HR, Guan L (2014) Structure-based mechanism for Na(+)/melibiose symport by MelB. Nat Commun 5:3009.  https://doi.org/10.1038/ncomms4009CrossRefPubMedPubMedCentralGoogle Scholar
  3. Granell M, Leon X, Leblanc G, Padros E, Lorenz-Fonfria VA (2010) Structural insights into the activation mechanism of melibiose permease by sodium binding. Proc Natl Acad Sci U S A 107:22078–22083.  https://doi.org/10.1073/pnas.1008649107CrossRefPubMedPubMedCentralGoogle Scholar
  4. Guan L, Nurva S, Ankeshwarapu SP (2011) Mechanism of melibiose/cation symport of the melibiose permease of Salmonella typhimurium. J Biol Chem 286:6367–6374.  https://doi.org/10.1074/jbc.M110.206227CrossRefPubMedGoogle Scholar
  5. Guan L, Jakkula SV, Hodkoff AA, Su Y (2012) Role of Gly117 in the cation/melibiose symport of MelB of Salmonella typhimurium. Biochemistry 51:2950–2957.  https://doi.org/10.1021/bi300230hCrossRefGoogle Scholar
  6. Hariharan P, Guan L (2014) Insights into the inhibitory mechanisms of the regulatory protein IIA(Glc) on melibiose permease activity. J Biol Chem 289:33012–33019.  https://doi.org/10.1074/jbc.M114.609255CrossRefPubMedPubMedCentralGoogle Scholar
  7. Hariharan P, Guan L (2017) Thermodynamic cooperativity of cosubstrate binding and cation selectivity of Salmonella typhimurium MelB. J Gen Physiol.  https://doi.org/10.1085/jgp.201711788
  8. Meyer-Lipp K, Sery N, Ganea C, Basquin C, Fendler K, Leblanc G (2006) The inner interhelix loop 4–5 of the melibiose permease from Escherichia coli takes part in conformational changes after sugar binding. J Biol Chem 281:25882–25892.  https://doi.org/10.1074/jbc.M601259200CrossRefGoogle Scholar
  9. Pourcher T, Bassilana M, Sarkar HK, Kaback HR, Leblanc G (1990) The melibiose/Na+ symporter of Escherichia coli: kinetic and molecular properties. Philos Trans R Soc Lond Ser B Biol Sci 326:411–423CrossRefGoogle Scholar
  10. Tokuda H, Kaback HR (1977) Sodium-dependent methyl 1-thio-β-d-galactopyranoside transport in membrane vesicles isolated from Salmonella typhimurium. Biochemistry 16:2130–2136CrossRefGoogle Scholar
  11. Wilson TH, Ding PZ (2001) Sodium-substrate cotransport in bacteria. Biochim Biophys Acta 1505:121–130.  https://doi.org/10.1016/S0005-2728(00)00282-6CrossRefPubMedGoogle Scholar

Copyright information

© European Biophysical Societies’ Association (EBSA) 2018

Authors and Affiliations

  1. 1.Department of Cell Physiology and Molecular Biophysics, Center for Membrane Protein ResearchTexas Tech University Health Sciences CenterLubbockUSA

Section editors and affiliations

  • Peter J. F. Henderson
    • 1
  1. 1.Astbury Centre for Structural Molecular Biology, Institute of Membrane and Systems BiologyUniversity of LeedsLeedsUK