|
Ribosome-inactivating Protein
A ribosome-inactivating protein (RIP) is a protein synthesis inhibitor that acts at the eukaryotic ribosome. This protein family describes a large family of such proteins that work by acting as rRNA N-glycosylase (EC 3.2.2.22). They inactivate 60S ribosomal subunits by an N-glycosidic cleavage, which releases a specific adenine base from the sugar-phosphate backbone of 28S rRNA. RIPs exist in bacteria and plants. Members of the family include shiga toxins, and type I (e.g. trichosanthin and luffin) and type II (e.g. ricin, agglutinin, and abrin) ribosome inactivating proteins (RIPs). All these toxins are structurally related. RIPs have been of considerable interest because of their potential use, conjugated with monoclonal antibodies, as immunotoxins to treat cancers. Further, trichosanthin has been shown to have potent activity against HIV-1-infected T cells and macrophages. Elucidation of the structure-function relationships of RIPs has therefore become a major research effort ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protein Synthesis Inhibitor
A protein synthesis inhibitor is a compound that stops or slows the growth or proliferation of cells by disrupting the processes that lead directly to the generation of new proteins. While a broad interpretation of this definition could be used to describe nearly any compound depending on concentration, in practice, it usually refers to compounds that act at the molecular level on translational machinery (either the ribosome itself or the translation factor), taking advantages of the major differences between prokaryotic and eukaryotic ribosome structures. Mechanism In general, protein synthesis inhibitors work at different stages of bacterial mRNA translation into proteins, like initiation, elongation (including aminoacyl tRNA entry, proofreading, peptidyl transfer, and bacterial translocation) and termination: Earlier stages * Rifamycin inhibits bacterial DNA transcription into mRNA by inhibiting DNA-dependent RNA polymerase by binding its beta-subunit. * alpha-Amanitin is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
T Cells
A T cell is a type of lymphocyte. T cells are one of the important white blood cells of the immune system and play a central role in the adaptive immune response. T cells can be distinguished from other lymphocytes by the presence of a T-cell receptor (TCR) on their cell surface. T cells are born from hematopoietic stem cells, found in the bone marrow. Developing T cells then migrate to the thymus gland to develop (or mature). T cells derive their name from the thymus. After migration to the thymus, the precursor cells mature into several distinct types of T cells. T cell differentiation also continues after they have left the thymus. Groups of specific, differentiated T cell subtypes have a variety of important functions in controlling and shaping the immune response. One of these functions is immune-mediated cell death, and it is carried out by two major subtypes: CD8+ "killer" and CD4+ "helper" T cells. (These are named for the presence of the cell surface proteins CD8 or ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phytolacca Americana
''Phytolacca americana'', also known as American pokeweed, pokeweed, poke sallet, dragonberries, and inkberry, is a poisonous, herbaceous perennial plant in the pokeweed family Phytolaccaceae. This pokeweed grows . It has simple leaves on green to red or purplish stems and a large white taproot. The flowers are green to white, followed by berries which ripen through red to purple to almost black which are a food source for songbirds such as gray catbird, northern mockingbird, northern cardinal, and brown thrasher, as well as other birds and some small non-avian animals (i.e., for species that are unaffected by its mammalian toxins). Pokeweed is native to eastern North America, the Midwest, and the South, with more scattered populations in the far West. It is also naturalized in parts of Europe and Asia. It is considered a pest species by farmers. Pokeweed is poisonous to humans, dogs, and livestock. In spring and early summer, shoots and leaves (not the root) are edible with pro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pokeweed Antiviral Protein
''Phytolacca americana'', also known as American pokeweed, pokeweed, poke sallet, dragonberries, and inkberry, is a poisonous, herbaceous perennial plant in the pokeweed family Phytolaccaceae. This pokeweed grows . It has simple leaves on green to red or purplish stems and a large white taproot. The flowers are green to white, followed by berries which ripen through red to purple to almost black which are a food source for songbirds such as gray catbird, northern mockingbird, northern cardinal, and brown thrasher, as well as other birds and some small non-avian animals (i.e., for species that are unaffected by its mammalian toxins). Pokeweed is native to eastern North America, the Midwest, and the South, with more scattered populations in the far West. It is also naturalized in parts of Europe and Asia. It is considered a pest species by farmers. Pokeweed is poisonous to humans, dogs, and livestock. In spring and early summer, shoots and leaves (not the root) are edible with pro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
European Mistletoe
''Viscum album'' is a species of mistletoe in the family Santalaceae, commonly known as European mistletoe, common mistletoe or simply as mistletoe (Old English ''mistle''). It is native to Europe and western and southern Asia. ''Viscum album'' is a hemiparasite on several species of trees, from which it draws water and nutrients. It has a significant role in European mythology, legends, and customs. In modern times, it is commonly featured in Christmas decoration and symbology. (''V. album'' is found only rarely in North America, as an introduced species; its cultural roles are usually fulfilled by the similar native species ''Phoradendron leucarpum''.) Description It is a parasitic plant, hemi-parasitic evergreen shrub, which grows on the stems of other trees. It has stems long with dichotomous branching. The leaf, leaves are in opposite pairs, strap-shaped, entire, leathery textured, long, broad and are a yellowish-green in colour. This species is dioecious and the insec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trichosanthin
Trichosanthin is a ribosome-inactivating protein. It is derived from ''Trichosanthes kirilowii''. It is also an abortifacient An abortifacient ("that which will cause a miscarriage" from Latin: ''abortus'' "miscarriage" and '' faciens'' "making") is a substance that induces abortion. This is a nonspecific term which may refer to any number of substances or medications, .... References External links * Proteins Ribosome-inactivating proteins {{pharmacology-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spiroplasma
''Spiroplasma'' is a genus of Mollicutes, a group of small bacteria without cell walls. ''Spiroplasma'' shares the simple metabolism, parasitic lifestyle, fried-egg colony morphology and small genome of other ''Mollicutes'', but has a distinctive helical morphology, unlike ''Mycoplasma''. It has a spiral shape and moves in a corkscrew motion. Many ''Spiroplasma'' are found either in the gut or haemolymph of insects where they can act to manipulate host reproduction, or defend the host as endosymbionts. ''Spiroplasma'' are also disease-causing agents in the phloem of plants. Spiroplasmas are fastidious organisms, which require a rich culture medium. Typically they grow well at 30 °C, but not at 37 °C. A few species, notably '' Spiroplasma mirum'', grow well at 37 °C (human body temperature), and cause cataracts and neurological damage in suckling mice. The best studied species of spiroplasmas are ''Spiroplasma poulsonii'', a reproductive manipulator and defensive ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shiga Toxin
Shiga toxins are a family of related toxins with two major groups, Stx1 and Stx2, expressed by genes considered to be part of the genome of lambdoid prophages. The toxins are named after Kiyoshi Shiga, who first described the bacterial origin of dysentery caused by ''Shigella dysenteriae''. Shiga-like toxin (SLT) is a historical term for similar or identical toxins produced by ''Escherichia coli''. The most common sources for Shiga toxin are the bacteria ''S. dysenteriae'' and some serotypes of ''Escherichia coli'' (STEC), which includes serotypes O157:H7, and O104:H4. Nomenclature Microbiologists use many terms to describe Shiga toxin and differentiate more than one unique form. Many of these terms are used interchangeably. # Shiga toxin type 1 and type 2 (Stx-1 and 2) are the Shiga toxins produced by some'' E. coli'' strains. Stx-1 is identical to Stx of ''Shigella spp.'' or differs by only one amino acid. Stx-2 shares 56% sequence identity with Stx-1. # Cytotoxin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Saporin
Saporin is a protein that is useful in biological research applications, especially studies of behavior. Saporins are so-called ribosome inactivating proteins (RIPs), due to its N-glycosidase activity, from the seeds of ''Saponaria officinalis'' (common name: soapwort). It was first described by Fiorenzo Stirpe and his colleagues in 1983 in an article that illustrated the unusual stability of the protein. Among the RIPs are some of the most toxic molecules known, such as ricin and abrin. Each of these toxins contain a second protein subunit, which inserts the RIP into a cell, enabling it to enzymatically inactivate the ribosomes, shutting down protein synthesis, stopping basic cell functions, resulting in cell death, and eventually causing death of the victim. Saporin has no chain capable of inserting it into the cell. Thus it and the soapwort plant are safe to handle. This has aided its use in research. If given a method of entry into the cell, saporin becomes a very potent to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ricin
Ricin ( ) is a lectin (a carbohydrate-binding protein) and a highly potent toxin produced in the seeds of the castor oil plant, ''Ricinus communis''. The median lethal dose (LD50) of ricin for mice is around 22 micrograms per kilogram of body weight via intraperitoneal injection. Oral exposure to ricin is far less toxic. An estimated lethal oral dose in humans is approximately 1 milligram per kilogram of body weight. Ricin was first described by Peter Hermann Stillmark, the founder of lectinology. Biochemistry Ricin is classified as a type 2 ribosome-inactivating protein (RIP). Whereas type 1 RIPs are composed of a single protein chain that possesses catalytic activity, type 2 RIPs, also known as holotoxins, are composed of two different protein chains that form a heterodimeric complex. Type 2 RIPs consist of an A chain that is functionally equivalent to a type 1 RIP, covalently connected by a single disulfide bond to a B chain that is catalytically inactive, but serves to m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Beetin
Beetin (BE27 or BE29) is a ribosome-inactivating protein found in the leaves of sugar beets, ''Beta vulgaris'' L, specifically attacking plant ribosomes. Sugar beet, beetins, that have been isolated meet all the criteria to be classified as single chain (type 1) ribosome inactivating proteins that are highly toxic to mammalian ribosomes but non-toxic to intact cultured mammalian cells. Beetin expression occurs when there is a viral infection of the plant. The different levels of glycosylation of the same polypeptide chain result in the two forms of beetin (BE27 or BE29). Beetin exhibits these two primary forms with apparent Mr values of 27 000 (BE27) and 29 000 (BE29) along with possessing glycan chains. Beetins are a type-I (single-chain) proteins with N-glycoside activity. Since it has been discovered that beetin is mostly concentrated in the intercellular fluid, its presence in the remaining parts of the leaf may be below the limit of detection rather than being nonexistent. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
_PDB_1r4q.png "Click for more on -> Shiga Toxin")
