Poster: Membrane Transport

Abs # 1228: 14-3-3 and H⁺-ATPase Isoforms Associated with the Arabidopsis Leaf Plasma Membrane

Presenter:	Alsterfjord, Magnus , magnus.alsterfjord@plantbio.lu.se
Authors	Alsterfjord, Magnus  (A)   Sehnke, Paul C (B)   Arkell, Annika  (A)   Ferl, Robert J (B)   Sommarin, Marianne  (A)   Larsson, Christer  (A)
Affiliations:	(A): Dept of Plant Biochemistry, Lund University (B): Dept of Horticultural Sciences, University of Florida

The plant plasma membrane is energized by a family of H⁺ pumping ATPases, which produce an electrochemical gradient across the membrane. There are 12 genes encoding plasma membrane H⁺-ATPases in the Arabidopsis genome and at least 11 of them are expressed. These H⁺-ATPases are activated by phosphorylation of the penultimate Thr in the C terminus and concomitant binding of 14-3-3 protein, which displaces the C-terminal autoinhibitory domain. 14-3-3s constitute a family of eukaryotic proteins that are key regulators of a large number of processes. 14-3-3s function as dimers and bind to particular (often phosphorylated) motifs in their target proteins. There are 15 genes encoding 14-3-3s in the Arabidopsis genome and at least 13 of them are expressed. In plants, 14-3-3s regulate major metabolic pathways by regulating enzymes such as nitrate reductase, sucrose phosphate synthase, starch synthase, and PM H⁺-ATPase. Using 14-3-3 overlays we now show that of all 12 14-3-3 isoforms tested, all are able to bind to the H+-ATPases expressed in the Arabidopsis leaf plasma membrane. However, using antibodies specific to 9 of these 14-3-3 isoforms we show that only a limited number of these are expressed in the leaf and bind to the plasma membrane. Similarly, using peptide mass fingerprinting we show that only a few of the H⁺-ATPase isoforms are expressed in the Arabidopsis leaf plasma membrane.