ABSTRACT
Homology of the amino acid sequence of the mitochondrial potassium-transporting protein (MW 57kDa), having the properties of a channel subunit of the mitochondrial ATP-dependent potassium channel, and calreticulin (MW 55kDa) was detected by MALDI-TOF-TOF analysis method. Inhibitory analysis of ATP-dependent potassium transport in mitochondria with polyclonal antibodies to calreticulin was carried out. A dose-dependent inhibition of potassium transport in mitochondria by these antibodies was shown. The maximum value of inhibition was 55-60%. Based on these data it is hypothesized that at least two types of ATP-sensitive potassium channels are localized in mitochdndrial membrane. It is expected that the type of mitochondrial ATP-dependent potassium channel, which includes homologous calreticulin protein is localized mainly at mitochondrial and reticulum membrane contact sites.
Subject(s)
Adenosine Triphosphatases/metabolism , Calbindin 2/metabolism , Cation Transport Proteins/metabolism , Mitochondria, Liver/metabolism , Mitochondrial Membranes/metabolism , Mitochondrial Proteins/metabolism , Animals , Antibodies/pharmacology , Calbindin 2/antagonists & inhibitors , Male , Mitochondrial Proteins/antagonists & inhibitors , Rats , Rats, Wistar , Spectrometry, Mass, Matrix-Assisted Laser Desorption-IonizationABSTRACT
The localization in the cell of the protein forming the ATP-dependent potassium-selective channels in the bilayer lipid membrane has been studied. The electron microscope investigation of rat liver and heart tissue sections after their incubation with Abs against this protein and the visualization of the protein with secondary Abs conjugated with colloid gold were carried out. Colloid gold particles were observed both in mitochondrial membranes and in membranes of endoplasmic and sarcoplasmic reticulum. In heart mitochondria, these particles were significantly greater than in liver mitochondria. The localization of the channel protein both in mitochondria and reticulum, as well as the structural similarity between the mitochondrial channel and the precursor of calreticulin suggest that the channel protein belongs to the family of calreticulins. The possible function of the protein as a channel subunit of the mitochondrial ATP-dependent potassium channel is discussed.
Subject(s)
Adenosine Triphosphate/physiology , Lipid Bilayers/metabolism , Mitochondria/metabolism , Potassium Channels/metabolism , Animals , Calreticulin/metabolism , Endoplasmic Reticulum/metabolism , Endoplasmic Reticulum/ultrastructure , Hepatocytes/metabolism , Hepatocytes/ultrastructure , In Vitro Techniques , Intracellular Membranes/metabolism , Intracellular Membranes/ultrastructure , Microscopy, Immunoelectron , Mitochondria/ultrastructure , Myocardium/metabolism , Myocardium/ultrastructure , RatsABSTRACT
Changes in the rate of respiration and functioning of the ATP-dependent potassium channel the liver and heart mitochondria of one-, three-, eight-, and twenty four-month-old Wistar male rats have been investigated. It was shown that the activity of the channel in the mitochondria of both tissues in 24-months-old animals decreases more than three times, and the content of potassium, 1.5-2 times compared with young one-month-old rats. The changes occur against the background of age-related decrease of energy supply in mitochondria, the respiratory complex-I underganig the greatest changes upon aging. The decrease of channel activity may be the result of changes in channel sensitivity to modulators and a decrease in the expression of mitochondrial K(+)-transporting channel-protein with a molecular mass of 5.5 kDa upon aging found in this work. As a result, the functioning of not only the mitoK(ATP) but also the whole mitochondrial potassium cycle is impaired.
