Related Experiment Video
Updated: Aug 8, 2026
05:47
Phosphoproteomic Strategy for Profiling Osmotic Stress Signaling in Arabidopsis
Published on: June 25, 2020
Protein phosphorylation in plant mitochondria
1Department of Agricultural Biochemistry, University of Nebraska, Lincoln, Nebraska 68583-0718.
Plant Physiology
|September 1, 1985
Summary
Plant mitochondria possess protein kinase activity, phosphorylating endogenous and exogenous proteins. This activity, observed across multiple plant species, suggests similarities with animal mitochondrial protein phosphorylation.
Area of Science:
- Biochemistry
- Plant Biology
- Cell Biology
Background:
- Mitochondria play crucial roles in cellular energy production and signaling.
- Protein phosphorylation is a key regulatory mechanism in eukaryotic cells.
- Understanding plant mitochondrial protein phosphorylation is essential for deciphering cellular processes.
Purpose of the Study:
- To investigate the presence and characteristics of protein kinase activity in plant mitochondria.
- To identify the substrates and regulatory properties of plant mitochondrial kinases.
- To compare plant mitochondrial protein phosphorylation with that of animal mitochondria.
Main Methods:
- Isolation of osmotically lysed mitochondria from various plant species (corn, pea, soybean, wheat, potato).
- In vitro kinase assays using adenosine triphosphate (ATP) and magnesium ions (Mg2+) to phosphorylate endogenous and exogenous proteins.
- Denaturing electrophoresis to analyze the molecular weight of phosphorylated polypeptides.
- Enzyme kinetic studies to determine optimal pH, ATP K(m), and the effect of various inhibitors.
Main Results:
- Protein kinase activity was detected in mitochondria from all tested plant species.
- Eight to fifteen endogenous mitochondrial polypeptides were phosphorylated, with a major 47,000 molecular weight polypeptide identified across species.
- Phosphorylation kinetics showed a biphasic pattern, rapid initially and slower thereafter.
- Optimal kinase activity occurred at neutral to alkaline pH, with an ATP K(m) of approximately 200 micromolar.
- The kinase was inhibited by calcium chloride (CaCl2) but unaffected by sodium fluoride (NaF), calmodulin, oligomycin, or cyclic adenosine monophosphate (cAMP).
Conclusions:
- Plant mitochondria exhibit significant protein kinase activity.
- The identified major phosphorylated polypeptide and kinase properties suggest conserved mechanisms.
- These findings indicate potential similarities between plant and animal mitochondrial protein phosphorylation pathways.
Related Concept Videos
01:02Phosphorylation
The addition or removal of phosphate groups from proteins is the most common chemical modification that regulates cellular processes. These modifications can affect the structure, activity, stability, and localization of proteins within cells as well as their interactions with other proteins.
During phosphorylation, protein kinases transfer the terminal phosphate group of ATP to specific amino acid side chains of substrate proteins. Serine, threonine, and tyrosine are the most commonly...
During phosphorylation, protein kinases transfer the terminal phosphate group of ATP to specific amino acid side chains of substrate proteins. Serine, threonine, and tyrosine are the most commonly...
02:54Protein Kinases and Phosphatases
Proteins undergo chemical modifications that trigger changes in the charge, structure, and conformation of the proteins. Phosphorylation, acetylation, glycosylation, nitrosylation, ubiquitination, lipidation, methylation, and proteolysis are various protein modifications that regulate protein activity. Such modifications are usually enzyme-driven.
Protein kinases
Many proteins in the cell are regulated by phosphorylation, the addition of a phosphate group. A family of enzymes called kinases...
Protein kinases
Many proteins in the cell are regulated by phosphorylation, the addition of a phosphate group. A family of enzymes called kinases...
01:19Translocation of Proteins into the Mitochondria
Mitochondrial precursors are translocated to the internal subcompartments via independent mechanisms involving distinct protein machineries called translocases.
Sorting of outer membrane proteins:
Mitochondrial outer membrane proteins are of two types: the transmembrane, beta-barrel porins, and the membrane-anchored, alpha-helical proteins. Beta-barrel porin precursors are translocated by the TOM complex and inserted into the outer mitochondrial membrane by the SAM complex. In contrast,...
Sorting of outer membrane proteins:
Mitochondrial outer membrane proteins are of two types: the transmembrane, beta-barrel porins, and the membrane-anchored, alpha-helical proteins. Beta-barrel porin precursors are translocated by the TOM complex and inserted into the outer mitochondrial membrane by the SAM complex. In contrast,...
01:31ATP Energy Storage and Release
ATP is a highly unstable molecule. Unless quickly used to perform work, ATP spontaneously dissociates into ADP and inorganic phosphate (Pi), and the free energy released during this process is lost as heat. The energy released by ATP hydrolysis is used to perform work inside the cell and depends on a strategy called energy coupling. Cells couple the exergonic reaction of ATP hydrolysis with endergonic reactions, allowing them to proceed.
One example of energy coupling using ATP involves a...
One example of energy coupling using ATP involves a...
01:37Energy to Drive Translocation
Mitochondrial protein import is powered by two distinct energy sources: ATP hydrolysis and electrochemical potential across the inner membrane. Newly synthesized precursors are bound by cytosolic chaperones of the Hsp70 family, which guide them to the import receptors on the mitochondrial surface. Utilizing the energy of ATP hydrolysis, Hsp70 chaperones transfer these precursors to the TOM receptors on the mitochondrial outer membrane.
Generally, polypeptides are unfolded by two distinct...
Generally, polypeptides are unfolded by two distinct...
01:27ATP Driven Pumps I: An Overview
ATP-driven pumps, also known as transport ATPases, are integral membrane proteins. They have binding sites for ATP located on the membrane's cytosolic side and the ion-conducting domain in the transmembrane region. These pumps use the free energy released from ATP hydrolysis to move the solutes across cell membranes against an electrochemical gradient.
There are four main types of ATP-driven pumps - P-type, V-type, F-type, and ABC transporter. All these pumps are of varying complexities and are...
There are four main types of ATP-driven pumps - P-type, V-type, F-type, and ABC transporter. All these pumps are of varying complexities and are...