Interactions of ATP, ADP and magnesium ion with rubisco activase and their effects on rubisco activation

Rubisco activase is a chloroplast protein that mediates a greatly enhanced activation of rubisco in the presence of ATP and Mg$\sp{2+}$. The fluorescent dye 1-anilinonaphthalene-8-sulfonate was used to study the binding of rubisco activase with ligands. The results indicated that rubisco activase bound ADP (k$\sb{\rm d}$ = 0.76 μM) more tightly than ATP (k$\sb{\rm d}$ = 41 μM). Alkaline medium (pH 8.0) and Mg$\sp{2+}$ (4 mM) favored binding of ATP, compared to ADP, to rubisco activase. Binding of ATP to the Mg$\sp{2+}$-protein complex also induced a transient increase in the tryptophan fluorescence of spinach rubisco activase. The kinetics of the fluorescence change was similar to that of ATP hydrolysis. ADP was a competitive inhibitor of the ATP induced fluorescence enhancement. This complex exhibited a higher molecular size ($>$600 kDa) than the enzyme-Mg-ADP complex (340 kDa) measured by gel permeation chromatography. Analysis of the initial catalytic rates of the enzyme indicated that aggregation of the rubisco activase-Mg-ATP complex was required for both ATP hydrolysis and rubisco activation.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Crop Sciences

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2011

Author dc:creator

• Wang, Zhen Yuan

Contributors dc:contributor

• Ogren, William L.

• Chemistry, Biochemistry
• Biology, Plant Physiology

Statement dc:rights

• Copyright 1992 Wang, Zhen Yuan

Language dc:language

eng

Identifier

AAI9215904
(UMI)AAI9215904

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/19685