Mutational Analysis of a Peripheral Pathway for Phospholipid Transport in ATP8A2: Poster at the 15th International Conference on Na,K-ATPase and Related Transport ATPases, Otsu, Japan, 2017

Research output: Contribution to conferencePosterResearch

  • Louise Mogensen
  • ,
  • Stine Mikkelsen
  • Rasmus Gantzel
  • Jonathan A. Coleman, Department of Biochemistry & Molecular Biology, University of British Columbia, Vancouver, BC, Canada
  • Bente Vilsen
  • Robert S. Molday, Department of Biochemistry & Molecular Biology, University of British Columbia, Vancouver, BC, Canada, Canada
  • Anna Lindeløv Vestergaard
  • ,
  • Jens Peter Andersen
ATP8A2 is a phosphatidylserine- and phosphatidylethanolamine-specific P4-ATPase that flips these phospholipids from the exoplasmic to the cytoplasmic membrane leaflet. However, the flippase transport mechanism is poorly understood, as phospholipids are about 10 times larger than the ions transported by the P2-ATPases (the “giant substrate problem”). Our previous studies pointed to a peripheral “hydrophobic gate” pathway for transport of the phospholipid head group in a groove between the transmembrane helices M1, 2, 4, and 6 [1]. Here, we have tested the peripheral pathway hypothesis by performing alanine scanning of residues in M1, M2, M3 and M4 of bovine ATP8A2. Residues proven interesting in the scan were further analyzed with respect to the importance of charge and size to understand their role in the transport mechanism. These include K122 and E126 in M2, which might interact with the phospholipid head group during transport and additionally participate in a hydrogen bond network with residues near the cytoplasmic end of M4. R82 and N85 placed around the kink of M1 where Ca2+ ions enter the Ca2+-ATPase were found important for PS interaction in the flippase in line with other evidence for conservation of classical transport elements from P2-ATPases. Moreover, T108 located at the exoplasmic end of M2 is critical to ATPase activity and lipid substrate affinity indicating that this residue could be part of an entry gate of the peripheral pathway. Overall, several findings in our study are compatible with the peripheral pathway hypothesis [1].

Reference
1. Vestergaard, A.L., et al., Proc Natl Acad Sci U S A, 2014. 111(14): p. E1334-43.



Original languageDanish
Publication year24 Sep 2017
Number of pages1
Publication statusPublished - 24 Sep 2017

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