ATP formation onset lag and post-illumination phosphorylation initiated with single-turnover flashes. II. Two modes of post-illumination phosphorylation driven by either delocalized or localized proton gradient coupling

1988 ◽  
Vol 20 (1) ◽  
pp. 107-128 ◽  
Author(s):  
William A. Beard ◽  
Gisela Chiang ◽  
Richard A. Dilley
Keyword(s):  
Proton Gradient ◽  
Single Turnover ◽  
Atp Formation ◽  
Gradient Coupling

Photophosphorylation as Function of ADP Concentration at Varying Transmembrane Proton Gradients

1989 ◽  
Vol 44 (5-6) ◽  
pp. 473-479 ◽  
Author(s):  
Georg Heinen ◽  
Heinrich Strotmann
Keyword(s):  
Steady State ◽  
Kinetic Model ◽  
Light Intensity ◽  
Phosphate Concentration ◽  
Proton Gradient ◽  
Enzyme Kinetic ◽  
Fluorescence Technique ◽  
Proton Gradients ◽  
Atp Formation ◽  
External Ph

Abstract Rates of photophosphorylation were measured at constant saturating phosphate concentration , varying ADP concentration , and varying light intensity. As the transmembrane proton gradient is decreased by phosphorylation to different extents depending on the concentration of ADP . rates of ATP formation obtained at the different ADP concentrations were plotted versus the actual steady state ΔpH (in the absence of ΔΨ) during the course of the reaction . ΔpH was monitored by the calibrated 9-aminoacridine fluorescence technique. In secondary plots phosphorylation as function of ADP concentration at different constant ΔpH values were obtained . The results indicate Michaelis-Menten kinetics. The true Km for ADP is virtually unaffected by ΔpH whereas Vmax (at ADP saturation ) strongly depends on ΔpH . The results are discussed in the framework of a simple enzyme kinetic model which considers the intrathylakoidal proton (at constant external pH ) as a third substrate for ATP formation. The model is capable o f explaining the reported results as well as a variety of important results from the literature.

scholarly journals Regulation of mitochondrial proteostasis by the proton gradient

2021 ◽  
Author(s):  
Maria Patron ◽  
Daryna Tarasenko ◽  
Hendrik Nolte ◽  
Mausumi Ghosh ◽  
Yohsuke Ohba ◽  
...  
Keyword(s):  
Protein Turnover ◽  
Mitochondrial Protein ◽  
Proton Gradient ◽  
Turnover Rates ◽  
Mitochondrial Proteome ◽  
Mitochondrial Inner Membrane ◽  
Proteomic Approach ◽  
Adaptive Processes ◽  
Respiratory Complex I ◽  
Gradient Coupling

Mitochondria adapt to different energetic demands reshaping their proteome. Mitochondrial proteases are emerging as key regulators of these adaptive processes. Here, we use a multi-proteomic approach to demonstrate regulation of the m-AAA protease AFG3L2 by the mitochondrial proton gradient, coupling mitochondrial protein turnover to the energetic status of mitochondria. We identify TMBIM5 (previously also known as GHITM or MICS1) as a Ca2+/H+ exchanger in the mitochondrial inner membrane, which binds to and inhibits the m-AAA protease. TMBIM5 ensures cell survival and respiration, allowing Ca2+ efflux from mitochondria and limiting mitochondrial hyperpolarization. Persistent hyperpolarization, however, triggers degradation of TMBIM5 and activation of the m-AAA protease. The m-AAA protease broadly remodels the mitochondrial proteome and mediates the proteolytic breakdown of respiratory complex I to confine ROS production and oxidative damage in hyperpolarized mitochondria. TMBIM5 thus integrates mitochondrial Ca2+ signaling and the energetic status of mitochondria with protein turnover rates to reshape the mitochondrial proteome and adjust the cellular metabolism.

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