Characteristics of the Mg2+-ATPase activity associated with the membrane-bound maize coupling factor

The membrane-bound coupling factor of maize mesophyll thylakoids is a latent ATPase. Mg2+-ATPase activity can be induced in the light with either dithiothreitol or low concentrations of trypsin. Maize thylakoids that are activated with light plus trypsin exhibit considerably higher levels of activit...

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Bibliographic Details
Published in:Plant physiology (Bethesda) 1989-11, Vol.91 (3), p.1107-1111
Main Author: Cohen, W.S. (University of Kentucky, Lexington, KY)
Format: Article
Language:English
Subjects:
ACTIVIDAD ENZIMATICA
ACTIVITE ENZYMATIQUE
Biological and medical sciences
Cell biochemistry
Cell physiology
Fundamental and applied biological sciences. Psychology
HIDROLASAS
HYDROLASE
MAGNESIO
MAGNESIUM
MEMBRANAS CELULARES
MEMBRANE CELLULAIRE
Membranes and Bioenergetics
MESOFILO
MESOPHYLLE
Plant physiology and development
PLASTE
PLASTIDIOS
ZEA MAYS
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Summary:The membrane-bound coupling factor of maize mesophyll thylakoids is a latent ATPase. Mg2+-ATPase activity can be induced in the light with either dithiothreitol or low concentrations of trypsin. Maize thylakoids that are activated with light plus trypsin exhibit considerably higher levels of activity in Na2SO3-dependent Mg2+-ATPase assays compared to thylakoids that are light and dithiothreitol activated (1400 micromoles per milligram of chlorophyll per hour versus 200 micromoles per milligram of chlorophyll per hour). Treatment with light and dithiothreitol or light plus trypsin were also required to demonstrate high levels of octyl glucoside-dependent Mg2+-ATPase activity in maize mesophyll thylakoids. Only small differences in octyl glucoside-dependent Mg2+-ATPase activity were observed in preparations that were activated in the light with either trypsin or dithiothreitol. Mg2+-ATPase activity can also be induced in maize mesophyll chloroplasts by illuminating intact preparations under appropriate conditions. Little or no ATPase activity was observed in the absence of illumination or in the presence of light plus methyl viologen. The active state decayed in the dark with a t1/2 of 6 to 7 minutes at room temperature. Based on the effect of the thiol oxidant, o-iodosobenzoate, and the uncoupler, nigericin, on the kinetics of deactivation of ATPase activity in intact maize chloroplasts, it appears that the activation process requires a transmembrane proton gradient and reduction of a key disulfide bridge in the gamma of chloroplast coupling factor one
ISSN:0032-0889
1532-2548
DOI:10.1104/pp.91.3.1107