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Secretion
440px Secretion is the movement of material from one point to another, such as a secreted chemical substance from a cell or gland. In contrast, excretion is the removal of certain substances or waste products from a cell or organism. The classical mechanism of cell secretion is via secretory portals at the plasma membrane called porosomes. Porosomes are permanent cup-shaped lipoprotein structures embedded in the cell membrane, where secretory vesicles transiently dock and fuse to release intra-vesicular contents from the cell. Secretion in bacterial species means the transport or translocation of effector molecules for example: proteins, enzymes or toxins (such as cholera toxin in pathogenic bacteria e.g. '' Vibrio cholerae'') from across the interior (cytoplasm or cytosol) of a bacterial cell to its exterior. Secretion is a very important mechanism in bacterial functioning and operation in their natural surrounding environment for adaptation and survival. In eukaryotic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Secretory Mechanism
440px Secretion is the movement of material from one point to another, such as a secreted chemical substance from a cell or gland. In contrast, excretion is the removal of certain substances or waste products from a cell or organism. The classical mechanism of cell secretion is via secretory portals at the plasma membrane called porosomes. Porosomes are permanent cup-shaped lipoprotein structures embedded in the cell membrane, where secretory vesicles transiently dock and fuse to release intra-vesicular contents from the cell. Secretion in bacterial species means the transport or translocation of effector molecules for example: proteins, enzymes or toxins (such as cholera toxin in pathogenic bacteria e.g. ''Vibrio cholerae'') from across the interior (cytoplasm or cytosol) of a bacterial cell to its exterior. Secretion is a very important mechanism in bacterial functioning and operation in their natural surrounding environment for adaptation and survival. In eukaryotic cells Me ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bacterial Secretion System
Bacterial secretion systems are protein complexes present on the cell membranes of bacteria for secretion of substances. Specifically, they are the cellular devices used by pathogenic bacteria to secrete their virulence factors (mainly of proteins) to invade the host cells. They can be classified into different types based on their specific structure, composition and activity. Generally, proteins can be secreted through two different processes. One process is a one-step mechanism in which proteins from the cytoplasm of bacteria are transported and delivered directly through the cell membrane into the host cell. Another involves a two-step activity in which the proteins are first transported out of the inner cell membrane, then deposited in the periplasm, and finally through the outer cell membrane into the host cell. These major differences can be distinguished between Gram-negative (diderm) and Gram-positive bacteria (monoderm). But the classification is by no means clear and com ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protein Targeting
:''This article deals with protein targeting in eukaryotes unless specified otherwise.'' Protein targeting or protein sorting is the biological mechanism by which proteins are transported to their appropriate destinations within or outside the cell. Proteins can be targeted to the inner space of an organelle, different intracellular membranes, the plasma membrane, or to the exterior of the cell via secretion. Information contained in the protein itself directs this delivery process. Correct sorting is crucial for the cell; errors or dysfunction in sorting have been linked to multiple diseases. History In 1970, Günter Blobel conducted experiments on protein translocation across membranes. Blobel, then an assistant professor at Rockefeller University, built upon the work of his colleague George Palade. Palade had previously demonstrated that non-secreted proteins were translated by free ribosomes in the cytosol, while secreted proteins (and target proteins, in general) were ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Porosome For Wiki-2
440px 280px Porosomes are cup-shaped supramolecular structures in the cell membranes of eukaryotic cells where secretory vesicles transiently dock in the process of vesicle fusion and secretion. The transient fusion of secretory vesicle membrane at the porosome base via SNARE proteins, result in the formation of a fusion pore or continuity for the release of intravesicular contents from the cell. After secretion is complete, the fusion pore temporarily formed at the base of the porosome is sealed. The porosomes are few nanometers in size and contain many different types of protein, especially chloride and calcium channels, actin, and SNARE proteins that mediate the docking and fusion of the vesicles with the cell membrane. Once the vesicles have docked with the SNARE proteins, they swell, which increases their internal pressure. They then transiently fuse at the base of the porosome, and these pressurized contents are ejected from the cell. Examination of cells following secr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Endoplasmic Reticulum
The endoplasmic reticulum (ER) is, in essence, the transportation system of the eukaryotic cell, and has many other important functions such as protein folding. It is a type of organelle made up of two subunits – rough endoplasmic reticulum (RER), and smooth endoplasmic reticulum (SER). The endoplasmic reticulum is found in most eukaryotic cells and forms an interconnected network of flattened, membrane-enclosed sacs known as cisternae (in the RER), and tubular structures in the SER. The membranes of the ER are continuous with the outer nuclear membrane. The endoplasmic reticulum is not found in red blood cells, or spermatozoa. The two types of ER share many of the same proteins and engage in certain common activities such as the synthesis of certain lipids and cholesterol. Different types of cells contain different ratios of the two types of ER depending on the activities of the cell. RER is found mainly toward the nucleus of cell and SER towards the cell membrane or pl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gland
In animals, a gland is a group of cells in an animal's body that synthesizes substances (such as hormones) for release into the bloodstream ( endocrine gland) or into cavities inside the body or its outer surface ( exocrine gland). Structure Development Every gland is formed by an ingrowth from an epithelial surface. This ingrowth may in the beginning possess a tubular structure, but in other instances glands may start as a solid column of cells which subsequently becomes tubulated. As growth proceeds, the column of cells may split or give off offshoots, in which case a compound gland is formed. In many glands, the number of branches is limited, in others (salivary, pancreas) a very large structure is finally formed by repeated growth and sub-division. As a rule, the branches do not unite with one another, but in one instance, the liver, this does occur when a reticulated compound gland is produced. In compound glands the more typical or secretory epithelium is found formi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Misfolded Proteins
Protein folding is the physical process by which a protein chain is translated to its native three-dimensional structure, typically a "folded" conformation by which the protein becomes biologically functional. Via an expeditious and reproducible process, a polypeptide folds into its characteristic three-dimensional structure from a random coil. Each protein exists first as an unfolded polypeptide or random coil after being translated from a sequence of mRNA to a linear chain of amino acids. At this stage the polypeptide lacks any stable (long-lasting) three-dimensional structure (the left hand side of the first figure). As the polypeptide chain is being synthesized by a ribosome, the linear chain begins to fold into its three-dimensional structure. Folding of many proteins begins even during translation of the polypeptide chain. Amino acids interact with each other to produce a well-defined three-dimensional structure, the folded protein (the right hand side of the figure) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chaperone (protein)
In molecular biology, molecular chaperones are proteins that assist the conformational folding or unfolding of large proteins or macromolecular protein complexes. There are a number of classes of molecular chaperones, all of which function to assist large proteins in proper protein folding during or after synthesis, and after partial denaturation. Chaperones are also involved in the translocation of proteins for proteolysis. The first molecular chaperones discovered were a type of assembly chaperones which assist in the assembly of nucleosomes from folded histones and DNA. One major function of molecular chaperones is to prevent the aggregation of misfolded proteins, thus many chaperone proteins are classified as heat shock proteins, as the tendency for protein aggregation is increased by heat stress. The majority of molecular chaperones do not convey any steric information for protein folding, and instead assist in protein folding by binding to and stabilizing folding inter ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glycosylation
Glycosylation is the reaction in which a carbohydrate (or 'glycan'), i.e. a glycosyl donor, is attached to a hydroxyl or other functional group of another molecule (a glycosyl acceptor) in order to form a glycoconjugate. In biology (but not always in chemistry), glycosylation usually refers to an enzyme-catalysed reaction, whereas glycation (also 'non-enzymatic glycation' and 'non-enzymatic glycosylation') may refer to a non-enzymatic reaction (though in practice, 'glycation' often refers more specifically to Maillard-type reactions). Glycosylation is a form of co-translational and post-translational modification. Glycans serve a variety of structural and functional roles in membrane and secreted proteins. The majority of proteins synthesized in the rough endoplasmic reticulum undergo glycosylation. Glycosylation is also present in the cytoplasm and nucleus as the ''O''-GlcNAc modification. Aglycosylation is a feature of engineered antibodies to bypass glycosylation. Fi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lumen (anatomy)
In biology, a lumen (plural lumina) is the inside space of a tubular structure, such as an artery or intestine. It comes . It can refer to: *The interior of a vessel, such as the central space in an artery, vein or capillary through which blood flows. *The interior of the gastrointestinal tract *The pathways of the bronchi in the lungs *The interior of renal tubules and urinary collecting ducts *The pathways of the female genital tract, starting with a single pathway of the vagina, splitting up in two lumina in the uterus, both of which continue through the Fallopian tubes In cell biology, a lumen is a membrane-defined space that is found inside several organelles, cellular components, or structures: *thylakoid, endoplasmic reticulum, Golgi apparatus, lysosome, mitochondrion, or microtubule Transluminal procedures ''Transluminal procedures'' are procedures occurring through lumina, including: * Natural orifice transluminal endoscopic surgery in the lumina of, for example, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
