Related Experiment Video
Updated: Jul 16, 2026
10:17
A Mass Spectrometry-Based Approach to Identify Phosphoprotein Phosphatases and their Interactors
Published on: April 29, 2022
Identification of a novel PP2C-type mitochondrial phosphatase
Mandar Joshi1, Nam Ho Jeoung, Kirill M Popov
1Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN 46202-5122, USA.
Biochemical and Biophysical Research Communications
|March 6, 2007
Summary
A newly identified mitochondrial phosphatase, belonging to the PP2C family, shows activity against a key enzyme in branched-chain amino acid metabolism. This discovery suggests a new regulatory role for mitochondrial phosphatases.
Area of Science:
- Biochemistry
- Molecular Biology
- Cell Biology
Background:
- Mitochondrial phosphatases play crucial roles in cellular metabolism and signaling.
- The PP2C (protein phosphatase 2 catalytic subunit) family is a major class of serine/threonine phosphatases.
- Understanding novel mitochondrial enzymes is key to elucidating complex metabolic pathways.
Purpose of the Study:
- To clone, characterize, and determine the subcellular localization of a novel phosphatase.
- To investigate the enzymatic activity and potential substrates of the novel phosphatase.
- To explore the tissue distribution and potential physiological roles of this mitochondrial enzyme.
Main Methods:
- Gene cloning and recombinant protein expression.
- Western blot analysis for protein expression and subcellular localization.
- Confocal microscopy using GFP-tagged protein.
- Enzymatic assays using branched-chain alpha-keto acid dehydrogenase complex as substrate.
Main Results:
- A novel phosphatase with a mitochondrial leader sequence was identified and cloned.
- The protein was confirmed to be localized in mitochondria using Western blot and confocal microscopy.
- The recombinant enzyme displayed manganese-dependent phosphoserine phosphatase activity towards the branched-chain alpha-keto acid dehydrogenase complex.
- Highest expression levels were detected in mouse brain, heart, liver, and kidney tissues.
Conclusions:
- The novel phosphatase is a mitochondrial enzyme belonging to the PP2C family.
- The enzyme likely participates in the regulation of branched-chain amino acid catabolism.
- Further research is needed to identify other mitochondrial substrates and fully elucidate the enzyme's function.
Related Concept Videos
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...
01:39Mitochondrial Precursor Proteins
Mitochondrial precursors are partially unfolded or loosely folded polypeptide chains. Newly synthesized precursors are inhibited from spontaneously folding into their native conformation by the cytosolic chaperones, heat shock proteins 70 (Hsp70), and mitochondrial import stimulation factors (MSFs). Precursors bound to MSFs are guided to the TOM70-TOM37 receptors, while precursors bound to Hsp70 chaperones are targetted to TOM20-TOM22 receptor complexes.
Most of the mitochondrial precursors...
Most of the mitochondrial precursors...
01:48ATP Synthase: Mechanism
In animals, the mitochondrial F1F0 ATP synthase is the key protein that synthesizes ATP molecules through a complex catalytic mechanism. While the nuclear genome encodes the majority of ATP synthase subunits, the mitochondrial genome encodes some of the enzyme's most critical components. The formation of this multi-subunit enzyme is a complex multi-step process regulated at the level of transcription, translation, and assembly. Defects in one or more of these steps can result in decreased ATP...
01:39Mitochondrial Protein Sorting
Mitochondria are double-membrane organelles of the eukaryotes involved in cellular metabolism, signaling, ATP synthesis, and programmed cell death. Each of these processes requires specific proteins and enzymes that must be correctly sorted to the right mitochondrial subcompartment for the proper functioning of the organelle.
Most of these mitochondrial proteins are encoded by the nucleus and imported to the mitochondria as unfolded or loosely folded precursors. Mitochondrial precursors...
Most of these mitochondrial proteins are encoded by the nucleus and imported to the mitochondria as unfolded or loosely folded precursors. Mitochondrial precursors...
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,...