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|Title:||Structural and functional analyses of PpENA1 provide insights into cation binding by type IID P-type ATPases in lower plants and fungi|
|Citation:||Biochimica et Biophysica Acta-Biomembranes, 2011; 1808(6):1483-1492|
|Publisher:||Elsevier Science BV|
|Damian P. Drew, Maria Hrmova, Christina Lunde, Andrew K. Jacobs, Mark Tester and Geoffrey B. Fincher|
|Abstract:||PpENA1 is a membrane-spanning transporter from the moss Physcomitrella patens, and is the first type IID P-type ATPase to be reported in the plant kingdom. In Physcomitrella, PpENA1 is essential for normal growth under moderate salt stress, while in yeast, type IID ATPases provide a vital efflux mechanism for cells under high salt conditions by selectively transporting Na+ or K+ across the plasma membrane. To investigate the structural basis for cation-binding within the type IID ATPase subfamily, we used homology modeling to identify a highly conserved cation-binding pocket between membrane helix (MH) 4 and MH 6 of the membrane-spanning pore of PpENA1. Mutation of specific charged and polar residues on MHs 4-6 resulted in a decrease or loss of protein activity as measured by complementation assays in yeast. The E298S mutation on MH 4 of PpENA1 had the most significant effect on activity despite the presence of a serine at this position in fungal type IID ATPases. Activity was partially restored in an inactivated PpENA1 mutant by the insertion of two additional serine residues on MH 4 and one on MH 6 based on the presence of these residues in fungal type IID ATPases. Our results suggest that the residues responsible for cation-binding in PpENA1 are distinct from those in fungal type IID ATPases, and that a fungal-type cation binding site can be successfully engineered into the moss protein.|
|Keywords:||Fungi; Saccharomyces cerevisiae; Bryopsida; Cations; Potassium; Sodium; Fungal Proteins; Plant Proteins; Immunoblotting; Genetic Complementation Test; Amino Acid Substitution; Binding Sites; Ion Transport; Amino Acid Sequence; Protein Structure, Secondary; Protein Structure, Tertiary; Protein Binding; Sequence Homology, Amino Acid; Mutation; Models, Molecular; Molecular Sequence Data; Sodium-Potassium-Exchanging ATPase|
|Rights:||© 2010 Elsevier B.V. All rights reserved.|
|Appears in Collections:||Agriculture, Food and Wine publications|
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