ARS | Publication request: Oxidation of an Adjacent Methionine Residue Inhibits Regulatory Seryl-phosphorylation of Pyruvate Dehydrogenase

Submitted to: Proteomics Insights
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 3, 2009
Publication Date: N/A

Interpretive Summary: Respiration is the use of energy by living cells to do work. Both growth and reproductive success are directly coupled to rates of respiration. As a result, respiration must be carefully controlled, or wasted energy would cause decreased crop yields and reduced agricultural productivity. The control of respiration in plant cells is a subject of ongoing study. Plant cells contain multiple forms of a protein thought to be important in overall control of respiration. During stress, this protein can be chemically modified. The modification affects control of protein activity. A method was developed that allows detailed chemical analysis of the protein modification. Plant cells were treated with chemicals that turn on the stress response, and the chemical analysis method was used to quantify effects of the stress. This information will be important to researchers in their attempts to increase agricultural productivity by altering the control of plant cell respiration, and to other plant scientists who will try to design more efficient crop plants through either classical breeding or biotechnology.

Technical Abstract: A Met residue is located adjacent to phosphorylation site 1 in the sequences of mitochondrial pyruvate dehydrogenase E1alpha subunits. When synthetic peptides including site 1 were treated with Hydrogen peroxide, the Met residue was oxidized to methionine sulfoxide (MetSO), and the peptides were no longer phosphorylated by E1alpha-kinase. Isolated mitochondria were incubated under state III or IV conditions, lysed, the pyruvate dehydrogenase complex (PDC) immunoprecipitated, and tryptic peptides analyzed by MALDI-TOF mass spectrometry. In all instances both Met and MetSO site 1 tryptic-peptides were detected. When suspension-cultured cells were incubated with chemical agents known to stimulate production of reactive oxygen species within the mitochondria there was no effect upon the amount of total PDC, but a significant decrease in the proportion of P-PDC. We propose that the redox-state of the Met residue proximal to phosphorylation site 1 of pyruvate dehydrogenase contributes to overall regulation of PDC activity in vivo.