PMID: 25568315

 

    Legend: Gene, Sites

Title : Interplay between disulfide bonding and N-glycosylation defines SLC4 Na+-coupled transporter extracellular topography

Abstract :
  1. The extracellular loop 3 (EL-3 ) of SLC4 Na(+)-coupled transporters contains 4 highly conserved cysteines and multiple N-glycosylation consensus sites
  2. In the electrogenic Na(+)-HCO3(-) cotransporter NBCe1-A , EL-3 is the largest extracellular loop and is predicted to consist of 82 amino acids
  3. To determine the structural-functional importance of the conserved cysteines and the N-glycosylation sites in NBCe1-A EL-3, we analyzed the potential interplay between EL-3 disulfide bonding and N-glycosylation and their roles in EL-3 topological folding
  4. Our results demonstrate that the 4 highly conserved cysteines form two intramolecular disulfide bonds, Cys(583)-Cys(585) and Cys(617)-Cys(642), respectively, that constrain EL-3 in a folded conformation
  5. The formation of the second disulfide bond is spontaneous and unaffected by the N-glycosylation state of EL-3 or the first disulfide bond, whereas formation of the first disulfide bond relies on the presence of the second disulfide bond and is affected by N-glycosylation
  6. Importantly, EL-3 from each monomer is adjacently located at the NBCe1-A dimeric interface
  7. When the two disulfide bonds are missing, EL-3 adopts an extended conformation highly accessible to protease digestion
  8. This unique adjacent parallel location of two symmetrically folded EL-3 loops from each monomer resembles a domain-like structure that is potentially important for NBCe1-A function in vivo
  9. Moreover, the formation of this unique structure is critically dependent on the finely tuned interplay between disulfide bonding and N-glycosylation in the membrane processed NBCe1-A dimer
Output (sent_index, trigger, protein, sugar, site):
  • 1. N-glycosylation, , -, -, sites
  • 3. N-glycosylation, , -, -, sites
  • 9. N-glycosylation, , NBCe1-A dimer, -, -
Output(Part-Of) (sent_index, protein, site):
  • 1. extracellular loop 3 (EL-3, cysteines
  • 1. extracellular loop 3 (EL-3, sites
*Output_Site_Fusion* (sent_index, protein, sugar, site):

 

 

Protein NCBI ID SENTENCE INDEX
NBCe1-A 8671 2,3,6,8
NBCe1-A dimer 8671 9
extracellular loop 3 (EL-3 6710 1