Responses to peroxynitrite in yeast: Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) as a sensitive intracellular target for nitration and enhancement of chaperone expression and ubiquitination

Peroxynitrite (ONOO-), a potent oxidizing and nitrating species, has been l inked to covalent modifications of biomolecules in a number of pathological conditions, In S, cerevisiae, a model eukaryotic cell system, ONOO- was fo und to be more potent than hydrogen peroxide in oxidizing thiols, inducing heat shock proteins (Hsp70) and enhancing the ubiquitination of proteins. A s identified by microsequence analysis following immunoprecipitation with a nti-nitrotyrosine antibodies, glyceraldehyde-3-phosphate dehydrogenase (GAP DH) was especially susceptible to nitration by ONOO- in yeast cells. The ac tivity of this enzyme was strongly inhibited upon steady-state exposure of the cells to low doses of ONOO- in yeast and in cultured rat astrocytes. Th us, ONOO- is a potent stressor in yeast Capable of inducing oxidative damag e and protein nitration, with GAPDH being a preferential target protein tha t is efficiently inactivated.