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Circular Permutation In Proteins
A circular permutation is a relationship between proteins whereby the proteins have a changed order of amino acids in their peptide sequence. The result is a protein structure with different connectivity, but overall similar three-dimensional (3D) shape. In 1979, the first pair of circularly permuted proteins – concanavalin A and lectin – were discovered; over 2000 such proteins are now known. Circular permutation can occur as the result of evolutionary events, posttranslational modifications, or protein engineering, artificially engineered mutations. The two main models proposed to explain the evolution of circularly permuted proteins are ''permutation by duplication'' and ''fission and fusion''. Permutation by duplication occurs when a gene undergoes gene duplication, duplication to form a tandem repeat, before redundant sections of the protein are removed; this relationship is found between prosaposin, saposin and swaposin. Fission and fusion occurs when partial proteins fu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Algorithm
In mathematics and computer science, an algorithm () is a finite sequence of Rigour#Mathematics, mathematically rigorous instructions, typically used to solve a class of specific Computational problem, problems or to perform a computation. Algorithms are used as specifications for performing calculations and data processing. More advanced algorithms can use Conditional (computer programming), conditionals to divert the code execution through various routes (referred to as automated decision-making) and deduce valid inferences (referred to as automated reasoning). In contrast, a Heuristic (computer science), heuristic is an approach to solving problems without well-defined correct or optimal results.David A. Grossman, Ophir Frieder, ''Information Retrieval: Algorithms and Heuristics'', 2nd edition, 2004, For example, although social media recommender systems are commonly called "algorithms", they actually rely on heuristics as there is no truly "correct" recommendation. As an e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antigen Presentation
Antigen presentation is a vital immune process that is essential for T cell immune response triggering. Because T cells recognize only fragmented antigens displayed on cell surfaces, antigen processing must occur before the antigen fragment can be recognized by a T-cell receptor. Specifically, the fragment, bound to the major histocompatibility complex (MHC), is transported to the surface of the antigen-presenting cell, a process known as presentation. If there has been an infection with viruses or bacteria, the antigen-presenting cell will present an endogenous or exogenous peptide fragment derived from the antigen by MHC molecules. There are two types of MHC molecules which differ in the behaviour of the antigens: MHC class I molecules (MHC-I) bind peptides from the cell cytosol, while peptides generated in the endocytic vesicles after internalisation are bound to MHC class II (MHC-II). Cellular membranes separate these two cellular environments - intracellular and extracell ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sphingolipid
Sphingolipids are a class of lipids containing a backbone of sphingoid bases, which are a set of aliphatic amino alcohols that includes sphingosine. They were discovered in brain extracts in the 1870s and were named after the mythological sphinx because of their enigmatic nature. These compounds play important roles in signal transduction and cell recognition. Sphingolipidoses, or disorders of sphingolipid metabolism, have particular impact on neural tissue. A sphingolipid with a terminal hydroxyl group is a ceramide. Other common groups bonded to the terminal oxygen atom include phosphocholine, yielding a sphingomyelin, and various sugar monomers or dimers, yielding cerebrosides and globosides, respectively. Cerebrosides and globosides are collectively known as glycosphingolipids. Structure The long-chain bases, sometimes simply known as sphingoid bases, are the first non-transient products of '' de novo'' sphingolipid synthesis in both yeast and mammals. These co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Saposin
Prosaposin, also known as PSAP, is a protein which in humans is encoded by the ''PSAP'' gene. This highly conserved glycoprotein is a precursor for 4 cleavage products: saposins A, B, C, and D. Saposin is an acronym for Sphingolipid Activator PrO ''SeINs. Each domain of the precursor protein is approximately 80 amino acid residues long with nearly identical placement of cysteine residues and glycosylation sites. Saposins A-D localize primarily to the lysosomal compartment where they facilitate the catabolism of glycosphingolipids with short oligosaccharide groups. The precursor protein exists both as a secretory protein and as an integral membrane protein and has neurotrophic activities. Saposins A–D are required for the hydrolysis of certain sphingolipids by specific lysosomal hydrolases. Family members * Saposin A was identified as an N-terminal domain in the prosaposin cDNA prior to its isolation. It is known to stimulate the enzymatic hydrolysis of 4-methylumbelliferyl-β ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Karolin Luger
Karolin Luger is an Austrian-American biochemist and biophysicist known for her work with nucleosomes and discovery of the three-dimensional structure of chromatin. She is a Distinguished Professor at the University of Colorado Boulder in the Biochemistry Department. Life Luger was born the youngest child after several brothers. Though not interested in mathematics, electronics, or physics, as her brothers were, she became fascinated with biology. She has stated that she chose a career in science during middle school, when she realized that "not everything was 'known' yet". As a young woman in Austria, Luger attended a gymnasium where she specialized in foreign languages. Luger is married and has one daughter. Education Luger earned a Bachelor of Science in microbiology and a Master of Science in biochemistry from the University of Innsbruck. She completed her Ph.D in biochemistry and biophysics at the University of Basel. Career In 1997, as a postdoc with Timothy J R ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trypsin
Trypsin is an enzyme in the first section of the small intestine that starts the digestion of protein molecules by cutting long chains of amino acids into smaller pieces. It is a serine protease from the PA clan superfamily, found in the digestive system of many vertebrates, where it hydrolyzes proteins. Trypsin is formed in the small intestine when its proenzyme form, the trypsinogen produced by the pancreas, is activated. Trypsin cuts peptide chains mainly at the carboxyl side of the amino acids lysine or arginine. It is used for numerous biotechnological processes. The process is commonly referred to as trypsinogen proteolysis or trypsinization, and proteins that have been digested/treated with trypsin are said to have been trypsinized. Trypsin was discovered in 1876 by Wilhelm Kühne. Although many sources say that Kühne named trypsin from the Ancient Greek word for rubbing, 'tripsis', because the enzyme was first isolated by rubbing the pancreas with glass powd ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cyclic Peptide
Cyclic peptides are polypeptide chains which contain a circular sequence of bonds. This can be through a connection between the amino and carboxyl ends of the peptide, for example in cyclosporin; a connection between the amino end and a side chain, for example in bacitracin; the carboxyl end and a side chain, for example in colistin; or two side chains or more complicated arrangements, for example in alpha-amanitin. Many cyclic peptides have been discovered in nature and many others have been synthesized in the laboratory. Their length ranges from just two amino acid residues to hundreds. In nature they are frequently antimicrobial or toxic; in medicine they have various applications, for example as antibiotics and immunosuppressive agents. Thin-layer chromatography, Thin-Layer Chromatography (TLC) is a convenient method to detect cyclic peptides in crude extract from bio-mass. Classification Cyclic peptides can be classified according to the types of bonds that comprise the ring ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemical Ligation
Chemical ligation is the chemoselective condensation of unprotected peptide segments enabled by the formation of a non-native bond at the ligation site. Chemical ligation is usually carried out in aqueous solution. Multiple consecutive chemical ligation reactions can be used to make proteins of the typical size found in Nature, i.e. with polypeptide chains containing 200–300 amino acids, produced by total synthesis. Principle of chemical ligation The "chemical ligation" concept was introduced by Kent in the early 1990s. It consisted of a novel approach to the covalent condensation of unprotected peptide segments by means of "unique, mutually reactive functionalities, one on each reacting peptide segment, designed to react only with each other and not with any of the functional groups found in (native) peptides". Chemical ligation of unprotected peptides is enabled by formation of an unnatural moiety, i.e. non-peptide bond, linking the two peptide segments in the ligation pro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Posttranslational Modification
In molecular biology, post-translational modification (PTM) is the covalent process of changing proteins following protein biosynthesis. PTMs may involve enzymes or occur spontaneously. Proteins are created by ribosomes, which translate mRNA into polypeptide chains, which may then change to form the mature protein product. PTMs are important components in cell signalling, as for example when prohormones are converted to hormones. Post-translational modifications can occur on the amino acid side chains or at the protein's C- or N- termini. They can expand the chemical set of the 22 amino acids by changing an existing functional group or adding a new one such as phosphate. Phosphorylation is highly effective for controlling the enzyme activity and is the most common change after translation. Many eukaryotic and prokaryotic proteins also have carbohydrate molecules attached to them in a process called glycosylation, which can promote protein folding and improve stability a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Concanavalin A Vs Lectin
Concanavalin A (ConA) is a lectin (carbohydrate-binding protein) originally extracted from the jack-bean (''Canavalia ensiformis''). It is a member of the legume lectin family. It binds specifically to certain structures found in various sugars, glycoproteins, and glycolipids, mainly internal and nonreducing terminal α-D- mannosyl and α-D-glucosyl groups. Its physiological function in plants, however, is still unknown. ConA is a plant mitogen, and is known for its ability to stimulate mouse T-cell subsets giving rise to four functionally distinct T cell populations, including precursors to regulatory T cells; a subset of human suppressor T-cells is also sensitive to ConA. ConA was the first lectin to be available on a commercial basis, and is widely used in biology and biochemistry to characterize glycoproteins and other sugar-containing entities on the surface of various cells. It is also used to purify glycosylated macromolecules in lectin affinity chromatography, as well as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protein Topology
Protein topology is a property of protein molecule that does not change under deformation (without cutting or breaking a bond). Frameworks Two main topology frameworks have been developed and applied to protein molecules. Knot Theory Knot theory which categorises chain entanglements. The usage of knot theory is limited to a small percentage of proteins as most of them are unknot. Circuit topology Circuit topology categorises intra-chain contacts based on their arrangements. Circuit topology is a determinant of protein folding kinetics and stability. Other Uses In biology literature, the term topology is also used to refer to mutual orientation of regular secondary structures, such as alpha-helices and beta strands in protein structure For example, two adjacent interacting alpha-helices or beta-s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
