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Helix Bundle
A helix bundle is a small protein fold composed of several alpha helices that are usually nearly parallel or antiparallel to each other. Three-helix bundles Three-helix bundles are among the smallest and fastest known cooperatively folding structural domains. The three-helix bundle in the villin headpiece domain is only 36 amino acids long and is a common subject of study in molecular dynamics simulations because its microsecond-scale folding time is within the timescales accessible to simulation. The 40-residue HIV accessory protein has a very similar fold and has also been the subject of extensive study. There is no general sequence motif associated with three-helix bundles, so they cannot necessarily be predicted from sequence alone. Three-helix bundles often occur in actin-binding proteins and in DNA-binding proteins. Four-helix bundles Four-helix bundles typically consist of four helices packed in a coiled-coil arrangement with a sterically close-packed hydrophobic core in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rop Protein
Rop (also known as repressor of primer, or as RNA one modulator (ROM)) is a small dimeric protein responsible for keeping the copy number of ColE1 family and related bacterial plasmids low in ''E. coli'' by increasing the speed of pairing between the preprimer RNA, RNA II, and its antisense RNA, RNA I. Structurally, Rop is a homodimeric four-helix bundle protein formed by the antiparallel interaction of two helix-turn-helix monomers. The Rop protein's structure has been solved to high resolution. Due to its small size and known structure, Rop has been used in protein design work to rearrange its helical topology and reengineer its loop regions. In general, the Helix_bundle#Four-helix_bundles, four-helix bundle has been extensively used in de novo protein design work as a simple model to understand the relationship between amino acid sequence and structure. External links Rop proteinfrom Proteopedia References {{protein-stub Proteins ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metabolic reactions, DNA replication, Cell signaling, responding to stimuli, providing Cytoskeleton, structure to cells and Fibrous protein, organisms, and Intracellular transport, transporting molecules from one location to another. Proteins differ from one another primarily in their sequence of amino acids, which is dictated by the Nucleic acid sequence, nucleotide sequence of their genes, and which usually results in protein folding into a specific Protein structure, 3D structure that determines its activity. A linear chain of amino acid residues is called a polypeptide. A protein contains at least one long polypeptide. Short polypeptides, containing less than 20–30 residues, are rarely considered to be proteins and are commonly called pep ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrophobic Core
The hydrophobic effect is the observed tendency of nonpolar substances to aggregate in an aqueous solution and to be excluded by water#Properties, water. The word hydrophobic literally means "water-fearing", and it describes the Segregation in materials, segregation of water and nonpolar substances, which maximizes the entropy of water and minimizes the area of contact between water and nonpolar molecules. In terms of thermodynamics, the hydrophobic effect is the free energy change of water surrounding a solute. A positive free energy change of the surrounding solvent indicates hydrophobicity, whereas a negative free energy change implies hydrophilicity. The hydrophobic effect is responsible for the separation of a mixture of oil and water into its two components. It is also responsible for effects related to biology, including: cell membrane and vesicle formation, protein folding, insertion of membrane proteins into the nonpolar lipid environment and protein-small molecule asso ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protein Design
Protein design is the rational design of new protein molecules to design novel activity, behavior, or purpose, and to advance basic understanding of protein function. Proteins can be designed from scratch (''de novo'' design) or by making calculated variants of a known protein structure and its sequence (termed ''protein redesign''). Rational protein design approaches make protein-sequence predictions that will fold to specific structures. These predicted sequences can then be validated experimentally through methods such as peptide synthesis, site-directed mutagenesis, or artificial gene synthesis. Rational protein design dates back to the mid-1970s. Recently, however, there were numerous examples of successful rational design of water-soluble and even transmembrane peptides and proteins, in part due to a better understanding of different factors contributing to protein structure stability and development of better computational methods. Overview and history The goal in ratio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lac Repressor
Lac may refer to: Places Africa * Lac Region, a district in Chad * Lac Prefecture, a district in Chad America * Rivière du Lac, a tributary of the Montmorency River, in Capitale-Nationale, Quebec, Canada Europe * Laç, a city in Albania * Lac, a village in Voloiac Commune, Mehedinţi County, Romania * Lac district, a district in the canton of Fribourg, Switzerland * Lancing railway station, a railway station in Sussex, England (station code: LAC) Elsewhere * Lac, a standard astronomical constellation abbreviation of Lacerta * Latin America and the Caribbean or LAC, a regional definition by the United Nations Other uses * Lac (resin), a resinous substance produced by insects **Shellac, the processed form of this resin * ''Lac'', French for lake (body of water) * ''lác'', an element in Anglo-Saxon names meaning "fight, play" *Lac, a character in Arthurian romance, father of Erec * LAC, the ICAO operator designator for Lockheed Corporation (Lockheed Aircraft Corporation), U ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cytokine
Cytokines () are a broad and loose category of small proteins (~5–25 kDa) important in cell signaling. Cytokines are produced by a broad range of cells, including immune cells like macrophages, B cell, B lymphocytes, T cell, T lymphocytes and mast cells, as well as Endothelium, endothelial cells, fibroblasts, and various stromal cells; a given cytokine may be produced by more than one type of cell. Due to their size, cytokines cannot cross the lipid bilayer of cells to enter the cytoplasm and therefore typically exert their functions by interacting with specific cytokine receptor, cytokine receptors on the target cell surface. Cytokines are especially important in the immune system; cytokines modulate the balance between humoral immunity, humoral and cell-mediated immunity, cell-based immune responses, and they regulate the maturation, growth, and responsiveness of particular cell populations. Some cytokines enhance or inhibit the action of other cytokines in complex way ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Human Growth Hormone
Growth hormone (GH) or somatotropin, also known as human growth hormone (hGH or HGH) in its human form, is a peptide hormone that stimulates growth, cell reproduction, and cell regeneration in humans and other animals. It is thus important in human development. GH also stimulates production of insulin-like growth factor 1 (IGF-1) and increases the concentration of glucose and free fatty acids. It is a type of mitogen which is specific only to the receptors on certain types of cells. GH is a 191-amino acid, single-chain polypeptide that is synthesized, stored and secreted by somatotropic cells within the lateral wings of the anterior pituitary gland. A recombinant form of HGH called somatropin ( INN) is used as a prescription drug to treat children's growth disorders and adult growth hormone deficiency. In the United States, it is only available legally from pharmacies by prescription from a licensed health care provider. In recent years in the United States, some health ca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ferritin
Ferritin is a universal intracellular and extracellular protein that stores iron and releases it in a controlled fashion. The protein is produced by almost all living organisms, including archaea, bacteria, algae, higher plants, and animals. It is the primary ''intracellular iron-storage protein'' in both prokaryotes and eukaryotes, keeping iron in a soluble and non-toxic form. In humans, it acts as a buffer against iron deficiency and iron overload. Ferritin is found in most tissues as a cytosolic protein, but small amounts are secreted into the serum where it functions as an iron carrier. Plasma ferritin is also an indirect marker of the total amount of iron stored in the body; hence, serum ferritin is used as a diagnostic test for iron-deficiency anemia and iron overload. Aggregated ferritin transforms into a water insoluble, crystalline and amorphous form of storage iron called hemosiderin. Ferritin is a globular protein complex consisting of 24 protein subuni ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cytochrome
Cytochromes are redox-active proteins containing a heme, with a central iron (Fe) atom at its core, as a cofactor. They are involved in the electron transport chain and redox catalysis. They are classified according to the type of heme and its mode of binding. Four varieties are recognized by the International Union of Biochemistry and Molecular Biology (IUBMB), cytochromes a, cytochromes b, cytochromes c and cytochrome d. Cytochrome function is linked to the reversible redox change from ferrous (Fe(II)) to the ferric (Fe(III)) oxidation state of the iron found in the heme core. In addition to the classification by the IUBMB into four cytochrome classes, several additional classifications such as cytochrome o and cytochrome P450 can be found in biochemical literature. History Cytochromes were initially described in 1884 by Charles Alexander MacMunn as respiratory pigments (myohematin or histohematin). In the 1920s, Keilin rediscovered these respiratory pigments and na ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protein Dimer
In biochemistry, a protein dimer is a macromolecular complex or protein multimer, multimer formed by two protein monomers, or single proteins, which are usually Non-covalent interaction, non-covalently bound. Many macromolecules, such as proteins or nucleic acids, form dimers. The word ''dimer'' has roots meaning "two parts", ''wikt:di-#Prefix, di-'' + ''wikt:-mer#Suffix, -mer''. A protein dimer is a type of protein quaternary structure. A protein homodimer is formed by two identical proteins while a protein heterodimer is formed by two different proteins. Most protein dimers in biochemistry are not connected by covalent bonds. An example of a non-covalent heterodimer is the enzyme reverse transcriptase, which is composed of two different amino acid chains. An exception is dimers that are linked by disulfide bridges such as the homodimeric protein IKBKG, NEMO. Some proteins contain specialized domains to ensure dimerization (dimerization domains) and specificity. The G protein- ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antiparallel (biochemistry)
In biochemistry, two biopolymers are antiparallel if they run parallel (geometry), parallel to each other but with opposite directionality (molecular biology), directionality (alignments). An example is the two complementarity (molecular biology), complementary strands of a DNA nucleic acid double helix, double helix, which antiparallel vectors, run in opposite directions alongside each other. Nucleic acids Nucleic acid molecules have a phosphoryl (5') end and a hydroxyl (3') end. This notation follows from IUPAC nomenclature of organic chemistry, organic chemistry nomenclature, and can be used to define the movement of enzymes such as DNA polymerases relative to the DNA strand in a non-arbitrary manner. G-quadruplexes G-quadruplexes, also known as G4 DNA are secondary structures found in nucleic acids that are rich in guanine. These structures are normally located at the telomeres (the ends of the Chromosome, chromosomes). The G-quadruplex can either be parallel or antiparallel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Globin Fold
The globins are a superfamily of heme-containing globular proteins, involved in binding and/or transporting oxygen. These proteins all incorporate the globin fold, a series of eight alpha helical segments. Two prominent members include myoglobin and hemoglobin. Both of these proteins reversibly bind oxygen via a heme prosthetic group. They are widely distributed in many organisms. Structure Globin superfamily members share a common three-dimensional fold. This 'globin fold' typically consists of eight alpha helices, although some proteins have additional helix extensions at their termini. Since the globin fold contains only helices, it is classified as an all-alpha protein fold. The globin fold is found in its namesake globin families as well as in phycocyanins. The globin fold was thus the first protein fold discovered (myoglobin was the first protein whose structure was solved). Helix packaging The eight helices of the globin fold core share significant nonlocal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
