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PPIF
Peptidyl-prolyl cis-trans isomerase, mitochondrial (PPIF) is an enzyme that in humans is encoded by the ''PPIF'' gene. It has also been referred to as, but should not be confused with, cyclophilin D (CypD), which is encoded by the '' PPID'' gene. As a member of the peptidyl-prolyl cis-trans isomerase (PPIase) family, this protein catalyzes the cis-trans isomerization of proline imidic peptide bonds, which allows it to facilitate folding or repair of proteins. PPIF is a major component of the mitochondrial permeability transition pore (MPTP) and, thus, highly involved in mitochondrial metabolism and apoptosis, as well as in mitochondrial diseases and related conditions, including cardiac diseases, neurodegenerative diseases, and muscular dystrophy. In addition, PPIF participates in inflammation, as well as in ischemic reperfusion injury, AIDS, and cancer. Structure Like other cyclophilins, PPIF forms a β-barrel structure with a hydrophobic core. This β-barrel is composed of ei ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Peptidylprolyl Isomerase D
Peptidylprolyl isomerase D (cyclophilin D), also known as PPID, is an enzyme which in humans is encoded by the ''PPID'' gene on chromosome 4. As a member of the peptidyl-prolyl cis-trans isomerase (PPIase) family, this protein catalyzes the cis-trans isomerization of proline imidic peptide bonds, which allows it to facilitate folding or repair of proteins. In addition, PPID participates in many biological processes, including mitochondrial metabolism, apoptosis, redox, and inflammation, as well as in related diseases and conditions, such as ischemic reperfusion injury, AIDS, and cancer. Structure Like other cyclophilins, PPID forms a β-barrel structure with a hydrophobic core. This β-barrel is composed of eight anti-parallel β-strands and capped by two α-helices at the top and bottom. In addition, the β-turns and loops in the strands contribute to the flexibility of the barrel. PPID in particular is composed of 370 residues and shares structural homology with PPIF, FKBP4, a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cyclophilin
Cyclophilins (CYPs) are a family of proteins named after their ability to bind to ciclosporin (cyclosporin A), an immunosuppressant which is usually used to suppress rejection after internal organ transplants. They are found in all domains of life. These proteins have peptidyl prolyl isomerase activity, which catalyzes the isomerization of peptide bonds from ''trans'' form to ''cis'' form at proline residues and facilitates protein folding. Cyclophilin A is a cytosolic and highly abundant protein. The protein belongs to a family of isozymes, including cyclophilins B and C, and natural killer cell cyclophilin-related protein. Major isoforms have been found within single cells, including inside the Endoplasmic reticulum, and some are even secreted. Mammalian cyclophilins Human genes encoding proteins containing the cyclophilin domain include: * PPIA, PPIB, PPIC, PPID, PPIE, PPIF, PPIG, PPIH * PPIL1, PPIL2, PPIL3, PPIL4, PPIAL4, PPIL6 * PPWD1 Cyclophilin A Cyclophilin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Enzyme
Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. Almost all metabolic processes in the cell need enzyme catalysis in order to occur at rates fast enough to sustain life. Metabolic pathways depend upon enzymes to catalyze individual steps. The study of enzymes is called ''enzymology'' and the field of pseudoenzyme analysis recognizes that during evolution, some enzymes have lost the ability to carry out biological catalysis, which is often reflected in their amino acid sequences and unusual 'pseudocatalytic' properties. Enzymes are known to catalyze more than 5,000 biochemical reaction types. Other biocatalysts are catalytic RNA molecules, called ribozymes. Enzymes' specificity comes from their unique three-dimensional structures. Like all catalysts, enzymes increase the reaction ra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Prolyl Isomerase
Prolyl isomerase (also known as peptidylprolyl isomerase or PPIase) is an enzyme () found in both prokaryotes and eukaryotes that interconverts the ''cis'' and ''trans'' isomers of peptide bonds with the amino acid proline. Proline has an unusually conformationally restrained peptide bond due to its cyclic structure with its side chain bonded to its secondary amine nitrogen. Most amino acids have a strong energetic preference for the ''trans'' peptide bond conformation due to steric hindrance, but proline's unusual structure stabilizes the ''cis'' form so that both isomers are populated under biologically relevant conditions. Proteins with prolyl isomerase activity include cyclophilin, FKBPs, and parvulin, although larger proteins can also contain prolyl isomerase structural domain, domains. Protein folding Proline is unique among the natural amino acids in having a relatively small difference in free energy between the ''cis'' configuration of its peptide bond and the more c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Caspase
Caspases (cysteine-aspartic proteases, cysteine aspartases or cysteine-dependent aspartate-directed proteases) are a family of protease enzymes playing essential roles in programmed cell death. They are named caspases due to their specific cysteine protease activity – a cysteine in its active site nucleophilically attacks and cleaves a target protein only after an aspartic acid residue. As of 2009, there are 12 confirmed caspases in humans and 10 in mice, carrying out a variety of cellular functions. The role of these enzymes in programmed cell death was first identified in 1993, with their functions in apoptosis well characterised. This is a form of programmed cell death, occurring widely during development, and throughout life to maintain cell homeostasis. Activation of caspases ensures that the cellular components are degraded in a controlled manner, carrying out cell death with minimal effect on surrounding tissues. Caspases have other identified roles in programmed cell ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Adenosine Triphosphate
Adenosine triphosphate (ATP) is an organic compound that provides energy to drive many processes in living cells, such as muscle contraction, nerve impulse propagation, condensate dissolution, and chemical synthesis. Found in all known forms of life, ATP is often referred to as the "molecular unit of currency" of intracellular energy transfer. When consumed in metabolic processes, it converts either to adenosine diphosphate (ADP) or to adenosine monophosphate (AMP). Other processes regenerate ATP. The human body recycles its own body weight equivalent in ATP each day. It is also a precursor to DNA and RNA, and is used as a coenzyme. From the perspective of biochemistry, ATP is classified as a nucleoside triphosphate, which indicates that it consists of three components: a nitrogenous base (adenine), the sugar ribose, and the Polyphosphate, triphosphate. Structure ATP consists of an adenine attached by the 9-nitrogen atom to the 1′ carbon atom of a sugar (ribose), which i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Depolarization
In biology, depolarization or hypopolarization is a change within a cell, during which the cell undergoes a shift in electric charge distribution, resulting in less negative charge inside the cell compared to the outside. Depolarization is essential to the function of many cells, communication between cells, and the overall physiology of an organism. Most cells in higher organisms maintain an internal environment that is negatively charged relative to the cell's exterior. This difference in charge is called the cell's membrane potential. In the process of depolarization, the negative internal charge of the cell temporarily becomes more positive (less negative). This shift from a negative to a more positive membrane potential occurs during several processes, including an action potential. During an action potential, the depolarization is so large that the potential difference across the cell membrane briefly reverses polarity, with the inside of the cell becoming positively char ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reactive Oxygen Species
In chemistry, reactive oxygen species (ROS) are highly reactive chemicals formed from diatomic oxygen (). Examples of ROS include peroxides, superoxide, hydroxyl radical, singlet oxygen, and alpha-oxygen. The reduction of molecular oxygen () produces superoxide (), which is the precursor to most other reactive oxygen species: :O2 + e^- -> \ ^\bullet O2- Dismutation of superoxide produces hydrogen peroxide (): :2 H+ + \ ^\bullet O2^- + \ ^\bullet O2^- -> H2O2 + O2 Hydrogen peroxide in turn may be partially reduced, thus forming hydroxide ions and hydroxyl radicals (), or fully reduced to water: :H2O2 + e^- -> HO^- + \ ^\bullet OH :2 H+ + 2 e- + H2O2 -> 2 H2O In a biological context, ROS are byproducts of the normal metabolism of oxygen. ROS have roles in cell signaling and homeostasis. ROS are intrinsic to cellular functioning, and are present at low and stationary levels in normal cells. In plants, ROS are involved in metabolic processes related to photoprotection and toleran ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Adenine Nucleotide Translocator
Adenine nucleotide translocator (ANT), also known as the ADP/ATP translocase (ANT), ADP/ATP carrier protein (AAC) or mitochondrial ADP/ATP carrier, exchanges free ATP with free ADP across the inner mitochondrial membrane. ANT is the most abundant protein in the inner mitochondrial membrane and belongs to mitochondrial carrier family. Free ADP is transported from the cytoplasm to the mitochondrial matrix, while ATP produced from oxidative phosphorylation is transported from the mitochondrial matrix to the cytoplasm, thus providing the cells with its main energy currency. ADP/ATP translocases are exclusive to eukaryotes and are thought to have evolved during eukaryogenesis. Human cells express four ADP/ATP translocases: SLC25A4, SLC25A5, SLC25A6 and SLC25A31, which constitute more than 10% of the protein in the inner mitochondrial membrane. These proteins are classified under the mitochondrial carrier superfamily. Types In humans, there exist three paraologous ANT isoforms: ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cyclosporin A
Ciclosporin, also spelled cyclosporine and cyclosporin, is a calcineurin inhibitor, used as an immunosuppressant medication. It is a natural product. It is taken orally or intravenously for rheumatoid arthritis, psoriasis, Crohn's disease, nephrotic syndrome, and in organ transplants to prevent rejection. It is also used as eye drops for keratoconjunctivitis sicca (dry eyes). Common side effects include high blood pressure, headache, kidney problems, increased hair growth, and vomiting. Other severe side effects include an increased risk of infection, liver problems, and an increased risk of lymphoma. Blood levels of the medication should be checked to decrease the risk of side effects. Use during pregnancy may result in preterm birth; however, ciclosporin does not appear to cause birth defects. Ciclosporin is believed to work by decreasing the function of lymphocytes. It does this by forming a complex with cyclophilin to block the phosphatase activity of calcineurin, w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parvulin
] Parvulin, a 92-amino acid protein discovered in E. coli in 1994,Rahfeld JU, Schierhorn A, Mann KH. (1994). A novel peptidyl-prolyl cis/trans isomerase from Escherichia coli. ''FEBS Lett'' 343:65. is the smallest known protein with prolyl isomerase activity, which catalyzes the ''cis''-''trans'' isomerization of proline peptide bonds. Although parvulin has no homology with larger prolyl isomerases such as cyclophilin and FKBP, it does share structural features with subdomains of other proteins involved in preparing secreted proteins for export from the cell.Balbach J, Schmid FX. (2000). Proline isomerizarion and its catalysis in protein folding. ''In Mechanisms of Protein Folding'' 2nd ed. Ed. RH Pain. ''Frontiers in Molecular Biology'' series. Oxford University Press: Oxford, UK. Although parvulin is as active as the larger prolyl isomerases against a short proline-containing test peptide, it has lower relative activity against biological substrates, possibly because the larger ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
FKBP
FKBP, or FK506 binding protein, is a family of proteins that have prolyl isomerase activity and are related to the cyclophilins in function, though not in amino acid sequence. FKBPs have been identified in many eukaryotes, ranging from yeast to humans, and function as protein folding chaperones for proteins containing proline residues. Along with cyclophilin, FKBPs belong to the immunophilin family. FKBP12 is notable in humans for binding the immunosuppressant molecule tacrolimus (originally designated FK506), which is used in treating patients after organ transplant and patients with autoimmune disorders. Tacrolimus has been found to reduce episodes of organ rejection over a related treatment, the drug ciclosporin, which binds cyclophilin. Both the FKBP-tacrolimus complex and the cyclosporin-cyclophilin complex inhibit a phosphatase called calcineurin, thus blocking signal transduction in the T-lymphocyte transduction pathway. This therapeutic role is not related to prolyl isome ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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