Ionic Locks in Melibiose Permease: Scope towards GLUT1 Deficiency Syndrome
| Autor: | Lan Guan, Anowarul Amin, Abdul S. Ethayathulla |
|---|---|
| Rok vydání: | 2014 |
| Předmět: |
0303 health sciences
Mutation Permease Chemistry Stereochemistry Mutant Melibiose transport Biophysics Periplasmic space medicine.disease_cause Major facilitator superfamily 03 medical and health sciences chemistry.chemical_compound 0302 clinical medicine Helix medicine Melibiose 030217 neurology & neurosurgery 030304 developmental biology |
| Zdroj: | Biophysical Journal. 106(2) |
| ISSN: | 0006-3495 |
| DOI: | 10.1016/j.bpj.2013.11.2079 |
| Popis: | The recently solved 3D crystal structures reveal that the Na+-coupled melibiose permease of Salmonella typhimurium (MelBSt) is a member of the Major Facilitator Superfamily (MFS). These inside-closed conformations show that Arg residues at positions 295 (Helix IX), 141 (Helix V), and 363 (Loop10-11) govern three clusters of electrostatic interactions for stabilizing the sealed internal cavity between N- and C-terminal domains at the cytoplasmic side. The cluster of these electrostatic interactions is designated as ionic lock. Except Lys at position 141 or 363, the replacement of R295, R141, or R363 individually with Cys, Gln, Glu, Leu, or Lys shows inhibition of active transport of melibiose to a level of 2 - 25 % of the WT, with little effect on the binding affinities for both sugar and Na+. Interestingly, a suppressor D35E mutation at the periplasmic end of helix I was spontaneously isolated from the R363Q mutant. Remarkably, introduction of D35E mutation with each conformation-compromised mutant of R295, R141 (except R141E), or R363 significantly rescues the melibiose transport to a level up to 90 % of the WT. However, D35E mutation fails to restore the activity if two lock sites are mutated by Cys simultaneously at any combination. Previous threading model of MelBSt at inside-open conformation show that all the three lock sites are at unlocked state. We conclude that these ionic locks are cooperative and involved in the transport-required global conformational changes by an alteration of locking and unlocking processes. Strikingly, these ionic locks are conserved in MFS permeases. Furthermore, they link with human diseases; e.g., some patients with GLUT1 Deficiency Syndrome are due to a single mutation of Arg at predicted ionic locks of the glucose transporter GLUT1 expressed in the blood-brain barrier. |
| Databáze: | OpenAIRE |
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