| 1. |
- Alsterfjord, Magnus, et al.
(author)
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Plasma membrane H+-ATPase and 14-3-3 Isoforms of Arabidopsis leaves: Evidence for isoform specificity in the 14-3-3/H+-ATPase interaction
- 2004
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In: Plant and Cell Physiology. - : Oxford University Press (OUP). - 1471-9053 .- 0032-0781. ; 45:9, s. 1202-1210
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Journal article (peer-reviewed)abstract
- The plasma membrane H+-ATPase is activated by binding of 14-3-3 protein to the phosphorylated C terminus. Considering the large number of 14-3-3 and H+-ATPase isoforms in Arabidopsis (13 and 11 expressed genes, respectively), specificity in binding may exist between 14-3-3 and H+-ATPase isoforms. We now show that the H'-ATPase is the main target for 14-3-3 binding at the plasma membrane, and that all twelve 14-3-3 istiforms tested bind to the H+-ATPase in vitro. Using specific antibodies for nine of the 14-3-3 isoforms, we show that GF14epsilon, mu, lambda, omega, chi, phi, nu, and upsilon are present in leaves, but that isolated plasma membranes lack GF14chi, phi and upsilon. Northern blots using isoform-specific probes for all 14-3-3 and H+-ATPase isoforms showed that transcripts were present for most of the isoforms. Based on mRNA levels, GF14epsilon, mu, lambda and chi are highly expressed 14-3-3 isoforms, and AHA1, 3, and 11 highly expressed H+-ATPase isoforms in leaves. However, mass peptide fingerprinting identified AHA1 and 2 with the highest score, and their presence could be confirmed by MS/MS. It may be calculated that under 'unstressed' conditions less than one percent of total 14-3-3 is attached to the H+-ATPase. However, during a condition requiring full activation of H+ pumping, as induced here by the presence of the fungal toxin fusicoccin, several percent of total 14-3-3 may be engaged in activation of the H+-ATPase.
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| 2. |
- Arkell, Annika
(author)
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The Arabidopsis 14-3-3 family -target protein specificity and expression of isoforms
- 2010
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Licentiate thesis (other academic/artistic)abstract
- 14-3-3 proteins comprise a family of highly conserved proteins. 14-3-3 proteins have been found in all organisms examined except for members of the prokaryotic kingdom. 14-3-3s are involved in numerous processes in the cell and they typically bind to phosphorylated motifs in other proteins and regulate their activities. In plants, 14-3-3 proteins are recognized as key regulators of primary metabolism and membrane transport. In Arabidopsis, there are 15 genes coding for 14-3-3s and hence several 14-3-3 isoforms may be present simultaneously in the plant. The aim of my work has been to understand why there are so many 14-3-3 isoforms. To investigate if there is specificity in 14-3-3/target protein interaction, the H+-ATPase/14-3-3 interaction was used as a model system. The study indicated some specificity but also a wide redundancy. To further analyse the question of specificity at different levels promoter:GUS fusions were utilized. The results clearly indicate a developmental, cell-, tissue- and organ-specific expression for all of the 14-3-3 isoforms in Arabidopsis. There is not a single case where the promoter of one isoform shows an expression that is identical to the expression of another isoform.
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