Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
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TY - JOUR
T1 - A study of the membrane association and regulatory effect of the phospholemman cytoplasmic domain
AU - Hughes, Eleri
AU - Whittaker, Christopher A P
AU - Barsukov, Igor L
AU - Esmann, Mikael
AU - Middleton, David A
N1 - Copyright © 2010. Published by Elsevier B.V.
PY - 2011/4
Y1 - 2011/4
N2 - Phospholemman (PLM) is a single-span transmembrane protein belonging to the FXYD family of proteins. PLM (or FXYD1) regulates the Na,K-ATPase (NKA) ion pump by altering its affinity for K(+) and Na(+) and by reducing its hydrolytic activity. Structural studies of PLM in anionic detergent micelles have suggested that the cytoplasmic domain, which alone can regulate NKA, forms a partial helix which is stabilized by interactions with the charged membrane surface. This work examines the membrane affinity and regulatory function of a 35-amino acid peptide (PLM(38-72)) representing the PLM cytoplasmic domain. Isothermal titration calorimetry and solid-state NMR measurements confirm that PLM(38-72) associates strongly with highly anionic phospholipid membranes, but the association is weakened substantially when the negative surface charge is reduced to a more physiologically relevant environment. Membrane interactions are also weakened when the peptide is phosphorylated at S68, one of the substrate sites for protein kinases. PLM(38-72) also lowers the maximal velocity of ATP hydrolysis (V(max)) by NKA, and phosphorylation of the peptide at S68 gives rise to a partial recovery of V(max). These results suggest that the PLM cytoplasmic domain populates NKA-associated and membrane-associated states in dynamic equilibrium and that phosphorylation may alter the position of the equilibrium. Interestingly, peptides representing the cytoplasmic domains of two other FXYD proteins, Mat-8 (FXYD3) and CHIF (FXYD4), have little or no interaction with highly anionic phospholipid membranes and have no effect on NKA function. This suggests that the functional and physical properties of PLM are not conserved across the entire FXYD family.
AB - Phospholemman (PLM) is a single-span transmembrane protein belonging to the FXYD family of proteins. PLM (or FXYD1) regulates the Na,K-ATPase (NKA) ion pump by altering its affinity for K(+) and Na(+) and by reducing its hydrolytic activity. Structural studies of PLM in anionic detergent micelles have suggested that the cytoplasmic domain, which alone can regulate NKA, forms a partial helix which is stabilized by interactions with the charged membrane surface. This work examines the membrane affinity and regulatory function of a 35-amino acid peptide (PLM(38-72)) representing the PLM cytoplasmic domain. Isothermal titration calorimetry and solid-state NMR measurements confirm that PLM(38-72) associates strongly with highly anionic phospholipid membranes, but the association is weakened substantially when the negative surface charge is reduced to a more physiologically relevant environment. Membrane interactions are also weakened when the peptide is phosphorylated at S68, one of the substrate sites for protein kinases. PLM(38-72) also lowers the maximal velocity of ATP hydrolysis (V(max)) by NKA, and phosphorylation of the peptide at S68 gives rise to a partial recovery of V(max). These results suggest that the PLM cytoplasmic domain populates NKA-associated and membrane-associated states in dynamic equilibrium and that phosphorylation may alter the position of the equilibrium. Interestingly, peptides representing the cytoplasmic domains of two other FXYD proteins, Mat-8 (FXYD3) and CHIF (FXYD4), have little or no interaction with highly anionic phospholipid membranes and have no effect on NKA function. This suggests that the functional and physical properties of PLM are not conserved across the entire FXYD family.
KW - Adenosine Triphosphate
KW - Amino Acid Sequence
KW - Animals
KW - Binding, Competitive
KW - Calorimetry
KW - Cell Membrane
KW - Circular Dichroism
KW - Humans
KW - Kinetics
KW - Lipid Bilayers
KW - Magnetic Resonance Spectroscopy
KW - Membrane Proteins
KW - Molecular Sequence Data
KW - Neoplasm Proteins
KW - Peptide Fragments
KW - Phospholipids
KW - Phosphoproteins
KW - Phosphorylation
KW - Potassium
KW - Protein Binding
KW - Serine
KW - Sodium
KW - Sodium-Potassium-Exchanging ATPase
U2 - 10.1016/j.bbamem.2010.11.024
DO - 10.1016/j.bbamem.2010.11.024
M3 - Journal article
C2 - 21130070
VL - 1808
SP - 1021
EP - 1031
JO - Biochimica et Biophysica Acta (BBA) - Biomembranes
JF - Biochimica et Biophysica Acta (BBA) - Biomembranes
SN - 0005-2736
IS - 4
ER -