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51-465: 56735 ENSG00000139648 ENSMUSG00000051879 Q3SY84 Q9R0H5 NM_033448 NM_019956 NP_258259 NP_064340 KRT71 is a keratin gene. Keratins are intermediate filament proteins responsible for the structural integrity of epithelial cells and are subdivided into epithelial keratins and hair keratins. This gene encodes a protein that is expressed in the inner root sheath of hair follicles . The type II keratins are clustered in
102-417: A fluorescent tag , also known as a fluorescent label or fluorescent probe , is a molecule that is attached chemically to aid in the detection of a biomolecule such as a protein, antibody, or amino acid. Generally, fluorescent tagging, or labeling, uses a reactive derivative of a fluorescent molecule known as a fluorophore . The fluorophore selectively binds to a specific region or functional group on
153-405: A chemical group associated with fluorescence. Since then, Fluorescein was created as a fluorescent dye by Adolph von Baeyer in 1871 and the method of staining was developed and utilized with the development of fluorescence microscopy in 1911. Ethidium bromide and variants were developed in the 1950s, and in 1994, fluorescent proteins or FPs were introduced. Green fluorescent protein or GFP
204-516: A different color based on its absorption. These include photoswitchable compounds, which are proteins that can switch from a non-fluorescent state to that of a fluorescent one given a certain environment. The most common organic molecule to be used as a photochrome is diarylethene . Other examples of photoswitchable proteins include PADRON-C, rs-FastLIME-s and bs-DRONPA-s, which can be used in plant and mammalian cells alike to watch cells move into different environments. Fluorescent biomaterials are
255-446: A genetic and structural level. The new term corneous beta protein (CBP) has been proposed to avoid confusion with α-keratins. Keratins (also described as cytokeratins ) are polymers of type I and type II intermediate filaments that have been found only in chordates ( vertebrates , amphioxi , urochordates ). Nematodes and many other non-chordate animals seem to have only type VI intermediate filaments , fibers that structure
306-495: A hybrid RNA + fluorescent is formed. The object of interest is attached to an enzyme that can recognize this hybrid DNA. Usually fluorescein is used as the fluorophore. Chemical labeling or the use of chemical tags utilizes the interaction between a small molecule and a specific genetic amino acid sequence. Chemical labeling is sometimes used as an alternative for GFP. Synthetic proteins that function as fluorescent probes are smaller than GFP's, and therefore can function as probes in
357-489: A means to label and identify biomolecules. Although fluorescent tagging in this regard has only been recently utilized, the discovery of fluorescence has been around for a much longer time. Sir George Stokes developed the Stokes Law of Fluorescence in 1852 which states that the wavelength of fluorescence emission is greater than that of the exciting radiation. Richard Meyer then termed fluorophore in 1897 to describe
408-429: A particular target. The development of methods to detect and identify biomolecules has been motivated by the ability to improve the study of molecular structure and interactions. Before the advent of fluorescent labeling, radioisotopes were used to detect and identify molecular compounds. Since then, safer methods have been developed that involve the use of fluorescent dyes or fluorescent proteins as tags or probes as
459-506: A possible way of using external factors to observe a pathway more visibly. The method involves fluorescently labeling peptide molecules that would alter an organism's natural pathway. When this peptide is inserted into the organism's cell, it can induce a different reaction. This method can be used, for example to treat a patient and then visibly see the treatment's outcome. Electrochemical sensors can be used for label-free sensing of biomolecules. They detect changes and measure current between
510-422: A probed metal electrode and an electrolyte containing the target analyte. A known potential to the electrode is then applied from a feedback current and the resulting current can be measured. For example, one technique using electrochemical sensing includes slowly raising the voltage causing chemical species at the electrode to be oxidized or reduced. Cell current vs voltage is plotted which can ultimately identify
561-526: A region of chromosome 12q13. This article on a gene on human chromosome 12 is a stub . You can help Misplaced Pages by expanding it . Keratin Keratin ( / ˈ k ɛr ə t ɪ n / ) is one of a family of structural fibrous proteins also known as scleroproteins . Alpha-keratin (α-keratin) is a type of keratin found in vertebrates . It is the key structural material making up scales , hair , nails , feathers , horns , claws , hooves , and
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#1732779923014612-424: A series of assembly steps beginning with dimerization; dimers assemble into tetramers and octamers and eventually, if the current hypothesis holds, into unit-length-filaments (ULF) capable of annealing end-to-end into long filaments. Cornification is the process of forming an epidermal barrier in stratified squamous epithelial tissue. At the cellular level, cornification is characterised by: Metabolism ceases, and
663-548: A short tag to minimize disruption of protein folding and function. Transition metals are used to link specific residues in the tags to site-specific targets such as the N-termini, C-termini, or internal sites within the protein. Examples of tags used for protein labeling include biarsenical tags, Histidine tags, and FLAG tags. Fluorescence in situ hybridization (FISH), is an example of a genetic labeling technique that utilizes probes that are specific for chromosomal sites along
714-405: A variety of conditions including keratosis , hyperkeratosis and keratoderma . Mutations in keratin gene expression can lead to, among others: Several diseases, such as athlete's foot and ringworm , are caused by infectious fungi that feed on keratin. Keratin is highly resistant to digestive acids if ingested. Cats regularly ingest hair as part of their grooming behavior , leading to
765-415: A wider variety of situations. Moreover, they offer a wider range of colors and photochemical properties. With recent advancements in chemical labeling, Chemical tags are preferred over fluorescent proteins due to the architectural and size limitations of the fluorescent protein's characteristic β-barrel. Alterations of fluorescent proteins would lead to loss of fluorescent properties. Protein labeling use
816-440: A β-keratin, can have these two as 75–80% of the total, with 10–15% serine , with the rest having bulky side groups. The chains are antiparallel, with an alternating C → N orientation. A preponderance of amino acids with small, nonreactive side groups is characteristic of structural proteins, for which H-bonded close packing is more important than chemical specificity . In addition to intra- and intermolecular hydrogen bonds ,
867-439: Is a naturally occurring fluorescent protein from the jellyfish Aequorea victoria that is widely used to tag proteins of interest. GFP emits a photon in the green region of the light spectrum when excited by the absorption of light. The chromophore consists of an oxidized tripeptide -Ser^65-Tyr^66-Gly^67 located within a β barrel. GFP catalyzes the oxidation and only requires molecular oxygen. GFP has been modified by changing
918-503: Is not itself fluorescent, but when it is bound by a specific protein or RNA structure becomes fluorescent. For instance, FAST is a variant of photoactive yellow protein which was engineered to bind chemical mimics of the GFP tripeptide chromophore. Likewise, the spinach aptamer is an engineered RNA sequence which can bind GFP chromophore chemical mimics, thereby conferring conditional and reversible fluorescence on RNA molecules containing
969-665: The hair (including wool ), the outer layer of skin , horns , nails , claws and hooves of mammals, and the slime threads of hagfish . The baleen plates of filter-feeding whales are also made of keratin. Keratin filaments are abundant in keratinocytes in the hornified layer of the epidermis ; these are proteins which have undergone keratinization . They are also present in epithelial cells in general. For example, mouse thymic epithelial cells react with antibodies for keratin 5, keratin 8, and keratin 14. These antibodies are used as fluorescent markers to distinguish subsets of mouse thymic epithelial cells in genetic studies of
1020-508: The spinnerets on spiders' tails, and the contributions of their interior glands , provide remarkable control of fast extrusion . Spider silk is typically about 1 to 2 micrometers (μm) thick, compared with about 60 μm for human hair, and more for some mammals. The biologically and commercially useful properties of silk fibers depend on the organization of multiple adjacent protein chains into hard, crystalline regions of varying size, alternating with flexible, amorphous regions where
1071-544: The thymus . The harder beta-keratins (β-keratins) are found only in the sauropsids , that is all living reptiles and birds . They are found in the nails, scales , and claws of reptiles , in some reptile shells ( Testudines , such as tortoise , turtle , terrapin ), and in the feathers , beaks , and claws of birds . These keratins are formed primarily in beta sheets . However, beta sheets are also found in α-keratins. Recent scholarship has shown that sauropsid β-keratins are fundamentally different from α-keratins at
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#17327799230141122-424: The toughness of keratinized tissue is chitin . Keratin comes in two types, the primitive, softer forms found in all vertebrates and harder, derived forms found only among sauropsids (reptiles and birds). Spider silk is classified as keratin, although production of the protein may have evolved independently of the process in vertebrates. Alpha-keratins (α-keratins) are found in all vertebrates. They form
1173-480: The Halo-tag. The Halo-tag covalently links to its ligand and allows for better expression of soluble proteins. Although fluorescent dyes may not have the same sensitivity as radioactive probes, they are able to show real-time activity of molecules in action. Moreover, radiation and appropriate handling is no longer a concern. With the development of fluorescent tagging, fluorescence microscopy has allowed
1224-417: The attached biosensor, light can be absorbed and emitted on a spectrophotometer . Additionally, biosensors that are fluorescent can be viewed with the naked eye. Some fluorescent biosensors also have the ability to change color in changing environments (ex: from blue to red). A researcher would be able to inspect and get data about the surrounding environment based on what color he or she could see visibly from
1275-458: The biosensor-molecule hybrid species. Colorimetric assays are normally used to determine how much concentration of one species there is relative to another. Photochromic compounds have the ability to switch between a range or variety of colors. Their ability to display different colors lies in how they absorb light. Different isomeric manifestations of the molecule absorbs different wavelengths of light, so that each isomeric species can display
1326-420: The cell and so are not generally used in cell imaging studies. Fluorescent labels can be hybridized to mRNA to help visualize interaction and activity, such as mRNA localization. An antisense strand labeled with the fluorescent probe is attached to a single mRNA strand, and can then be viewed during cell development to see the movement of mRNA within the cell. A fluorogen is a ligand (fluorogenic ligand) which
1377-480: The cells are almost completely filled by keratin. During the process of epithelial differentiation, cells become cornified as keratin protein is incorporated into longer keratin intermediate filaments. Eventually the nucleus and cytoplasmic organelles disappear, metabolism ceases and cells undergo a programmed death as they become fully keratinized. In many other cell types, such as cells of the dermis, keratin filaments and other intermediate filaments function as part of
1428-505: The chains are randomly coiled . A somewhat analogous situation occurs with synthetic polymers such as nylon , developed as a silk substitute. Silk from the hornet cocoon contains doublets about 10 μm across, with cores and coating, and may be arranged in up to 10 layers, also in plaques of variable shape. Adult hornets also use silk as a glue , as do spiders. Glues made from partially-hydrolysed keratin include hoof glue and horn glue . Abnormal growth of keratin can occur in
1479-444: The coiled-coil structure is hydrophobic interactions between apolar residues along the keratins helical segments. Limited interior space is the reason why the triple helix of the (unrelated) structural protein collagen , found in skin , cartilage and bone , likewise has a high percentage of glycine . The connective tissue protein elastin also has a high percentage of both glycine and alanine . Silk fibroin , considered
1530-470: The crystal structure of a helical domain of keratins. The human genome has 54 functional annotated Keratin genes, 28 are in the Keratin type 1 family, and 26 are in the Keratin type 2 family. Fibrous keratin molecules supercoil to form a very stable, left-handed superhelical motif to multimerise, forming filaments consisting of multiple copies of the keratin monomer . The major force that keeps
1581-449: The cytoskeleton to mechanically stabilize the cell against physical stress. It does this through connections to desmosomes, cell–cell junctional plaques, and hemidesmosomes, cell-basement membrane adhesive structures. Cells in the epidermis contain a structural matrix of keratin, which makes this outermost layer of the skin almost waterproof, and along with collagen and elastin gives skin its strength. Rubbing and pressure cause thickening of
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1632-435: The distinguishing feature of keratins is the presence of large amounts of the sulfur -containing amino acid cysteine , required for the disulfide bridges that confer additional strength and rigidity by permanent, thermally stable crosslinking —in much the same way that non-protein sulfur bridges stabilize vulcanized rubber . Human hair is approximately 14% cysteine. The pungent smells of burning hair and skin are due to
1683-444: The exact defined change that these isotopes incur on the peptides, it is possible to tell through the spectrometry graph which peptides contained the isotopes. By doing so, one can extract the protein of interest from several others in a group. Isotopic compounds play an important role as photochromes, described below. Biosensors are attached to a substance of interest. Normally, this substance would not be able to absorb light, but with
1734-405: The gradual formation of hairballs that may be expelled orally or excreted. In humans, trichophagia may lead to Rapunzel syndrome , an extremely rare but potentially fatal intestinal condition. Keratin expression is helpful in determining epithelial origin in anaplastic cancers. Tumors that express keratin include carcinomas , thymomas , sarcomas and trophoblastic neoplasms . Furthermore,
1785-581: The length of a chromosome, also known as chromosome painting . Multiple fluorescent dyes that each have a distinct excitation and emission wavelength are bound to a probe which is then hybridized to chromosomes. A fluorescence microscope can detect the dyes present and send it to a computer that can reveal the karyotype of a cell. This technique allows abnormalities such as deletions and duplications to be revealed. Chemical tags have been tailored for imaging technologies more so than fluorescent proteins because chemical tags can localize photosensitizers closer to
1836-883: The nucleus . The human genome encodes 54 functional keratin genes , located in two clusters on chromosomes 12 and 17. This suggests that they originated from a series of gene duplications on these chromosomes. The keratins include the following proteins of which KRT23 , KRT24 , KRT25 , KRT26 , KRT27 , KRT28 , KRT31 , KRT32 , KRT33A , KRT33B , KRT34 , KRT35 , KRT36 , KRT37 , KRT38 , KRT39 , KRT40 , KRT71 , KRT72 , KRT73 , KRT74 , KRT75 , KRT76 , KRT77 , KRT78 , KRT79 , KRT8 , KRT80 , KRT81 , KRT82 , KRT83 , KRT84 , KRT85 and KRT86 have been used to describe keratins past 20. The first sequences of keratins were determined by Israel Hanukoglu and Elaine Fuchs (1982, 1983). These sequences revealed that there are two distinct but homologous keratin families, which were named type I and type II keratins. By analysis of
1887-580: The outer layer of skin among vertebrates. Keratin also protects epithelial cells from damage or stress. Keratin is extremely insoluble in water and organic solvents. Keratin monomers assemble into bundles to form intermediate filaments , which are tough and form strong unmineralized epidermal appendages found in reptiles , birds , amphibians , and mammals . Excessive keratinization participate in fortification of certain tissues such as in horns of cattle and rhinos , and armadillos ' osteoderm . The only other biological matter known to approximate
1938-710: The outer, cornified layer of the epidermis and form protective calluses, which are useful for athletes and on the fingertips of musicians who play stringed instruments. Keratinized epidermal cells are constantly shed and replaced. These hard, integumentary structures are formed by intercellular cementing of fibers formed from the dead, cornified cells generated by specialized beds deep within the skin. Hair grows continuously and feathers molt and regenerate. The constituent proteins may be phylogenetically homologous but differ somewhat in chemical structure and supermolecular organization. The evolutionary relationships are complex and only partially known. Multiple genes have been identified for
1989-401: The precise expression-pattern of keratin subtypes allows prediction of the origin of the primary tumor when assessing metastases . For example, hepatocellular carcinomas typically express CK8 and CK18, and cholangiocarcinomas express CK7, CK8 and CK18, while metastases of colorectal carcinomas express CK20, but not CK7. Fluorescent tag In molecular biology and biotechnology ,
2040-404: The primary structures of these keratins and other intermediate filament proteins, Hanukoglu and Fuchs suggested a model in which keratins and intermediate filament proteins contain a central ~310 residue domain with four segments in α-helical conformation that are separated by three short linker segments predicted to be in beta-turn conformation. This model has been confirmed by the determination of
2091-433: The quantity of chemical species consumed or produced at the electrode. Fluorescent tags can be used in conjunction with electrochemical sensors for ease of detection in a biological system. Of the various methods of labeling biomolecules, fluorescent labels are advantageous in that they are highly sensitive even at low concentration and non-destructive to the target molecule folding and function. Green fluorescent protein
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2142-473: The sequence. Fluorescent labeling is known for its non-destructive nature and high sensitivity. This has made it one of the most widely used methods for labeling and tracking biomolecules. Several techniques of fluorescent labeling can be utilized depending on the nature of the target. In enzymatic labeling, a DNA construct is first formed, using a gene and the DNA of a fluorescent protein. After transcription,
2193-409: The surface of many cell types. It has been proposed that keratins can be divided into 'hard' and 'soft' forms, or ' cytokeratins ' and 'other keratins'. That model is now understood to be correct. A new nuclear addition in 2006 to describe keratins takes this into account. Keratin filaments are intermediate filaments . Like all intermediate filaments, keratin proteins form filamentous polymers in
2244-414: The target molecule and can be attached chemically or biologically. Various labeling techniques such as enzymatic labeling, protein labeling , and genetic labeling are widely utilized. Ethidium bromide , fluorescein and green fluorescent protein are common tags. The most commonly labelled molecules are antibodies, proteins, amino acids and peptides which are then used as specific probes for detection of
2295-427: The target proteins. Proteins can then be labeled and detected with imaging such as super-resolution microscopy , Ca -imaging , pH sensing, hydrogen peroxide detection, chromophore assisted light inactivation, and multi-photon light microscopy. In vivo imaging studies in live animals have been performed for the first time with the use of a monomeric protein derived from the bacterial haloalkane dehalogenase known as
2346-663: The use of colorimetric biosensors, photochromic compounds, biomaterials , and electrochemical sensors. Fluorescent labeling is also a common method in which applications have expanded to enzymatic labeling, chemical labeling, protein labeling , and genetic labeling. There are currently several labeling methods for tracking biomolecules. Some of the methods include the following. Common species that isotope markers are used for include proteins. In this case, amino acids with stable isotopes of either carbon, nitrogen, or hydrogen are incorporated into polypeptide sequences. These polypeptides are then put through mass spectrometry . Because of
2397-427: The visualization of specific proteins in both fixed and live cell images. Localization of specific proteins has led to important concepts in cellular biology such as the functions of distinct groups of proteins in cellular membranes and organelles. In live cell imaging, fluorescent tags enable movements of proteins and their interactions to be monitored. Latest advances in methods involving fluorescent tags have led to
2448-1084: The volatile sulfur compounds formed. Extensive disulfide bonding contributes to the insolubility of keratins, except in a small number of solvents such as dissociating or reducing agents. The more flexible and elastic keratins of hair have fewer interchain disulfide bridges than the keratins in mammalian fingernails , hooves and claws (homologous structures), which are harder and more like their analogs in other vertebrate classes. Hair and other α-keratins consist of α-helically coiled single protein strands (with regular intra-chain H-bonding ), which are then further twisted into superhelical ropes that may be further coiled. The β-keratins of reptiles and birds have β-pleated sheets twisted together, then stabilized and hardened by disulfide bridges. Thiolated polymers (= thiomers ) can form disulfide bridges with cysteine substructures of keratins getting covalently attached to these proteins. Thiomers exhibit therefore high binding properties to keratins found in hair, on skin and on
2499-829: The wavelength of light absorbed to include other colors of fluorescence. YFP or yellow fluorescent protein , BFP or blue fluorescent protein , and CFP or cyan fluorescent protein are examples of GFP variants. These variants are produced by the genetic engineering of the GFP gene. Synthetic fluorescent probes can also be used as fluorescent labels. Advantages of these labels include a smaller size with more variety in color. They can be used to tag proteins of interest more selectively by various methods including chemical recognition-based labeling, such as utilizing metal-chelating peptide tags, and biological recognition-based labeling utilizing enzymatic reactions. However, despite their wide array of excitation and emission wavelengths as well as better stability, synthetic probes tend to be toxic to
2550-452: The β-keratins in feathers, and this is probably characteristic of all keratins. The silk fibroins produced by insects and spiders are often classified as keratins, though it is unclear whether they are phylogenetically related to vertebrate keratins. Silk found in insect pupae , and in spider webs and egg casings, also has twisted β-pleated sheets incorporated into fibers wound into larger supermolecular aggregates. The structure of
2601-474: Was discovered by Osamu Shimomura in the 1960s and was developed as a tracer molecule by Douglas Prasher in 1987. FPs led to a breakthrough of live cell imaging with the ability to selectively tag genetic protein regions and observe protein functions and mechanisms. For this breakthrough, Shimomura was awarded the Nobel Prize in 2008. New methods for tracking biomolecules have been developed including
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