Proceedings of the XLVII Italian Society of Agricultural Genetics - SIGA Annual Congress

Verona, Italy - 24/27 September, 2003

ISBN 88-900622-4-X

Poster Abstract - 5.23

EFFECT OF THE REMOVAL OF THE C-TERMINAL REGION OF GF14-6, A MAIZE 14-3-3 PROTEIN, IN THE INTERACTION WITH THE H⁺-ATPASE

S. VISCONTI, P. ADUCCI

Dipartimento di Biologia, Università di Roma “Tor Vergata”, Roma

14-3-3 proteins, H⁺-ATPase, protein-protein interaction

14-3-3 are a family of conserved proteins widespread in all eukaryotes. They are involved in the regulation of many cellular processes, such as the cell division and differentiation, apoptosis, gene transcription, targeting of proteins to cellular compartments and in the coordination of multiple signal transduction pathways.

In plants, 14-3-3 proteins possess also some peculiar features; in fact they are involved in the regulation of metabolic enzymes, among which the nitrate reductase and the sucrose-phosphate synthase, and in the regulation of the H⁺-ATPase, the most important ion pump present in the plasma membrane of plant cells. Recently, a role of 14-3-3 proteins in germination, senescence and in plant responses to abiotic and biotic stresses has been suggested.

These functions are always ascribable to the ability of 14-3-3 to interact with target proteins. Generally, the interaction with 14-3-3 proteins requires the phosphorylation of specific serine/threonine residues present in the 14-3-3-binding motif, even though some proteins are able to interact with 14-3-3 in a phosphorylation-independent manner.

An amphipathic groove responsible of binding with target proteins has been identified by crystallization studies and mutants analysis of 14-3-3. Recently it has been suggested that the C-terminal region of 14-3-3 proteins could play a regulatory role in the interaction with target proteins by occupying the intramolecular ligand-binding groove. Interestingly, the selectively cleavage of the C-terminal region of a 14-3-3 isoform has been observed during germination of barley embryos; suggesting that the C terminus removal could represent a post-translational regulation mechanism of the 14-3-3 proteins.

In order to investigate about the role of the C-terminal region of the GF14-6, a maize 14-3-3 isoform, we produced a mutant lacking of the last 22 amino acid residues and expressed it in Escherichia coli as a GST-fusion protein. The deletion mutant was then tested for the ability to interact with the H⁺-ATPase and to stimulate its activity.