|Tovar-Mendez, A - UNIV OF MISSOURI-COLUMBIA|
|Randall, D - UNIV OF MISSOURI-COLUMBIA|
|Emerich, D - UNIV OF MISSOURI-COLUMBIA|
Submitted to: American Society of Plant Biologists Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: July 3, 2001
Publication Date: N/A
Technical Abstract: Pyruvate dehydrogenase kinase (PDK) is the primary regulator of flux through the mitochondrial pyruvate dehydrogenase complex (PDC). The primary amino acid sequence indicates these kinases have the five domains characteristic of prokaryotic two-component histidine kinases. Chemical modification with histidine directed reagents inactivates the PDK suggesting a possible role for histidines in PDK catalysis (Mooney, B.P., et al. (2000) Biochem. Biophys. Res. Commun. 267, 500-503). Although, PDKs phosphorylate on serine residues to determine the possibility of a histidine-serine phosphotransfer in the PDK catalyzed reaction, we mutated the two potential phosphotransfer histidine residues (H121 and H168 in the Arabidopsis thaliana PDK sequence) since they are conserved in all the known PDK and BCDK sequences, and they are N-terminal to the catalytic domain, as is the case for the phosphotransfer histidine of histidine kinases sequences. Previous results in our laboratory indicated that the H121Q mutant was partiality active (Thelen, J.J., et al. (2000) Biochem. J. 349, 195-201); suggesting that either H121 is not the sole phosphotransfer histidine residue or that mutagenesis of H121 exposes and additional, otherwise cryptic, phosphotransfer histidine residue such as the H168. However, we show that in contrast to the prediction of the hypothesis neither the H168 mutation or the double mutation of H121/168 abolished the AtPDK activity. The results rule out a role for H121 and for H168 as phosphotransfer histidines in PDK and indicate that the Arabidopsis thaliana PDK autophosphorylation is not related to the E1a trans- phosphorylation.