Mechanism of Photoinactivation of Plant Plasma Membrane Atpase

Abstract

UV radiation at 290 and 365 nm inactivates two forms of the K+‐stimulated ATPase associated with the plasma membrane of suspension‐cultured cells of Rosa damascena. One form is 15 and 36 times more sensitive than the other to 290 and 365 nm, respectively. For both forms, the inactivation requires oxygen, is inhibited by azide and diazobicyclo(2.2.2.2)octane, but not glycerol, and is enhanced up to 7.5 times in deuterium oxide solvent. Inactivation occurs concomitantly with loss of absorbance at 290 nm. Cs+ and NO−3, quenchers of tryptophan fluorescence, inhibit inactivation. The results suggest that inactivation involves singlet‐oxygen mediated destruction of tryptophans in the ATPases.

Photoinactivation of Superoxide Synthases of the Plasma Membrane from Rose (Rosa damascena Mill.) Cells

“…Thus the data indicate that the mechanism of inactivation of the 02synthases at 300 nm did not depend on the generation of singlet oxygen. These findings are very different from the results of experiments on another rose plasma membrane enzyme, the H+-ATF'ase, in which tryptophans appear to be the principal photoreceptors and the mechanism of inactivation depends strongly on singlet oxygen ( 15). Thus there is no evidence for a common photosensitizing agent in the plasma membrane preparation.…”

Ultraviolet light and ozone stimulate accumulation of salicylic acid, pathogenesis-related proteins and virus resistance in tobacco

“…The effect of these abiotic agents on SA levels and disease resistance appears to mimic that of necrotizing pathogens, suggesting that biotic and abiotic inducers of SA accumulation and disease resistance may share a common signal-transduction pathway. For example, it is known that UV light, ozone and necrotizing pathogens elicit a burst of activated oxygen species in plant tissues (Imbrie and Murphy 1984;Heath 1988;Apostol et al 1989;Dixon and Lamb 1990). However, it remains to be determined if oxygen radicals are linked to the induction of SA biosynthesis and acquired disease resistance.…”

Ultraviolet Radiation and Plants: Burning Questions

“…A third UV radiation response for which there is some mechanistic information is the destruction of a rose cell plasma membrane ATPase by UV-6 radiation. The action spectrum of this response peaks at 290 nm (Murphy, 1983), and the fluence-response curve shows that this response occurs at fluences that are typical of sunlight (Imbrie and Murphy, 1984). The inactivation of ATPase probably results from singlet oxygen-mediated destruction of tryptophan residues in the ATPase protein (Imbrie and Murphy, 1984).…”