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Dna Topoisomerase Iv
Topoisomerase IV is one of two Type II topoisomerases in bacteria, the other being DNA gyrase. Like gyrase, topoisomerase IV is able to pass one double-strand of DNA through another double-strand of DNA, thereby changing the linking number of DNA by two in each enzymatic step. Both share a hetero-4-mer structure formed by a symmetric homodimer of A/B heterodimers, usually named ''ParC'' and ''ParE''. Functions Topoisomerase IV has two functions in the cell. * First, it is responsible for unlinking, or decatenating, DNA following DNA replication. The double-helical nature of DNA and its semiconservative mode of replication causes the two newly replicated DNA strands to be interlinked. These links must be removed in order for the chromosome (and plasmids) to segregate into daughter cells so that cell division can complete. * Topoisomerase IV's second function in the cell is to relax positive supercoils. It shares this role with DNA gyrase, which is also able to relax positive superco ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Type II Topoisomerase
Type II topoisomerases are topoisomerases that cut both strands of the DNA helix simultaneously in order to manage DNA tangles and supercoils. They use the hydrolysis of ATP, unlike Type I topoisomerase. In this process, these enzymes change the linking number of circular DNA by ±2. Topoisomerases are ubiquitous enzymes, found in all living organisms. In animals, topoisomerase II is a chemotherapy target. In prokaryotes, gyrase is an antibacterial target. Indeed, these enzymes are of interest for a wide range of effects. Function Type II topoisomerases increase or decrease the linking number of a DNA loop by 2 units, and it promotes chromosome disentanglement. For example, DNA gyrase, a type II topoisomerase observed in '' E. coli'' and most other prokaryotes, introduces negative supercoils and decreases the linking number by 2. Gyrase is also able to remove knots from the bacterial chromosome. Along with gyrase, most prokaryotes also contain a second type IIA topoisomerase, t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DNA Gyrase
DNA gyrase, or simply gyrase, is an enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products ... within the class of topoisomerase and is a subclass of Type II topoisomerases that reduces topological strain in an ATP dependent manner while double-stranded DNA is being unwound by elongating RNA polymerase, RNA-polymerase or by helicase in front of the progressing DNA replication#Replication fork, replication fork. The enzyme causes negative DNA supercoil, supercoiling of the DNA or relaxes positive supercoils. It does so by looping the template so as to form a crossing, then cutting one of the double helices and passing the other through it before releasing the break, changing the linking number by two in each enzymatic step. This process occurs in bacteria, whose single circular DNA is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Linking Number
In mathematics, the linking number is a numerical invariant that describes the linking of two closed curves in three-dimensional space. Intuitively, the linking number represents the number of times that each curve winds around the other. In Euclidean space, the linking number is always an integer, but may be positive or negative depending on the orientation of the two curves (this is not true for curves in most 3-manifolds, where linking numbers can also be fractions or just not exist at all). The linking number was introduced by Gauss in the form of the linking integral. It is an important object of study in knot theory, algebraic topology, and differential geometry, and has numerous applications in mathematics and science, including quantum mechanics, electromagnetism, and the study of DNA supercoiling. Definition Any two closed curves in space, if allowed to pass through themselves but not each other, can be moved into exactly one of the following standard positions. Thi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DNA Replication
In molecular biology, DNA replication is the biological process of producing two identical replicas of DNA from one original DNA molecule. DNA replication occurs in all living organisms acting as the most essential part for biological inheritance. This is essential for cell division during growth and repair of damaged tissues, while it also ensures that each of the new cells receives its own copy of the DNA. The cell possesses the distinctive property of division, which makes replication of DNA essential. DNA is made up of a double helix of two complementary strands. The double helix describes the appearance of a double-stranded DNA which is thus composed of two linear strands that run opposite to each other and twist together to form. During replication, these strands are separated. Each strand of the original DNA molecule then serves as a template for the production of its counterpart, a process referred to as semiconservative replication. As a result of semi-conservative rep ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Semiconservative
Semiconservative replication describe the mechanism of DNA replication in all known cells. DNA replication occurs on multiple origins of replication along the DNA template strand (antinsense strand). As the DNA double helix is unwound by helicase, replication occurs separately on each template strand (sense strand) in antiparallel directions. This process is known as semi-conservative replication because two copies of the original DNA molecule are produced, each copy conserving (replicating) the information from one half of the original DNA molecule. Each copy contains one original strand and one newly-synthesized strand. (Both copies should be identical, but this is not entirely assured.) The structure of DNA (as deciphered by James D. Watson and Francis Crick in 1953) suggested that each strand of the double helix would serve as a template for synthesis of a new strand. It was not known how newly synthesized strands combined with template strands to form two double helical DNA m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chromosome
A chromosome is a long DNA molecule with part or all of the genetic material of an organism. In most chromosomes the very long thin DNA fibers are coated with packaging proteins; in eukaryotic cells the most important of these proteins are the histones. These proteins, aided by chaperone proteins, bind to and condense the DNA molecule to maintain its integrity. These chromosomes display a complex three-dimensional structure, which plays a significant role in transcriptional regulation. Chromosomes are normally visible under a light microscope only during the metaphase of cell division (where all chromosomes are aligned in the center of the cell in their condensed form). Before this happens, each chromosome is duplicated ( S phase), and both copies are joined by a centromere, resulting either in an X-shaped structure (pictured above), if the centromere is located equatorially, or a two-arm structure, if the centromere is located distally. The joined copies are now called si ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plasmids
A plasmid is a small, extrachromosomal DNA molecule within a cell that is physically separated from chromosomal DNA and can replicate independently. They are most commonly found as small circular, double-stranded DNA molecules in bacteria; however, plasmids are sometimes present in archaea and eukaryotic organisms. In nature, plasmids often carry genes that benefit the survival of the organism and confer selective advantage such as antibiotic resistance. While chromosomes are large and contain all the essential genetic information for living under normal conditions, plasmids are usually very small and contain only additional genes that may be useful in certain situations or conditions. Artificial plasmids are widely used as vectors in molecular cloning, serving to drive the replication of recombinant DNA sequences within host organisms. In the laboratory, plasmids may be introduced into a cell via transformation. Synthetic plasmids are available for procurement over the intern ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Supercoil
DNA supercoiling refers to the amount of twist in a particular DNA strand, which determines the amount of strain on it. A given strand may be "positively supercoiled" or "negatively supercoiled" (more or less tightly wound). The amount of a strand’s supercoiling affects a number of biological processes, such as compacting DNA and regulating access to the genetic code (which strongly affects DNA metabolism and possibly gene expression). Certain enzymes, such as topoisomerases, change the amount of DNA supercoiling to facilitate functions such as DNA replication and transcription. The amount of supercoiling in a given strand is described by a mathematical formula that compares it to a reference state known as "relaxed B-form" DNA. Overview In a "relaxed" double-helical segment of B-DNA, the two strands twist around the helical axis once every 10.4–10.5 base pairs of sequence. Adding or subtracting twists, as some enzymes do, imposes strain. If a DNA segment under twist ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DNA Polymerase
A DNA polymerase is a member of a family of enzymes that catalyze the synthesis of DNA molecules from nucleoside triphosphates, the molecular precursors of DNA. These enzymes are essential for DNA replication and usually work in groups to create two identical DNA duplexes from a single original DNA duplex. During this process, DNA polymerase "reads" the existing DNA strands to create two new strands that match the existing ones. These enzymes catalyze the chemical reaction : deoxynucleoside triphosphate + DNAn pyrophosphate + DNAn+1. DNA polymerase adds nucleotides to the three prime (3')-end of a DNA strand, one nucleotide at a time. Every time a cell divides, DNA polymerases are required to duplicate the cell's DNA, so that a copy of the original DNA molecule can be passed to each daughter cell. In this way, genetic information is passed down from generation to generation. Before replication can take place, an enzyme called helicase unwinds the DNA molecule from its tightl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Journal Of Biological Chemistry
The ''Journal of Biological Chemistry'' (''JBC'') is a weekly peer-reviewed scientific journal that was established in 1905., jbc.org Since 1925, it is published by the American Society for Biochemistry and Molecular Biology. It covers research in areas of biochemistry and molecular biology. The editor is Alex Toker. As of January 2021, the journal is fully open access. In press articles are available free on its website immediately after acceptance. Editors The following individuals have served as editors of the journal: * 1906–1909: John Jacob Abel and Christian Archibald Herter * 1909–1910: Christian Archibald Herter * 1910–1914: Alfred Newton Richards * 1914–1925: Donald D. Van Slyke * 1925–1936: Stanley R. Benedict. After Benedict died, John T. Edsall served as temporary editor until the next editor was appointed. * 1937–1958: Rudolph J. Anderson * 1958–1967: John T. Edsall * 1968–1971: William Howard Stein * 1971–2011: Herbert Tabor * 2011–2015: ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nucleic Acids Research
''Nucleic Acids Research'' is an open-access peer-reviewed scientific journal published since 1974 by the Oxford University Press. The journal covers research on nucleic acids, such as DNA and RNA, and related work. According to the ''Journal Citation Reports'', the journal's 2021 impact factor is 19.160. The journal publishes two yearly special issues, the first issue of each year is dedicated to biological databases, published in January since 1993, and the other is devoted to papers describing web-based software resources of value to the biological community (web server A web server is computer software and underlying hardware that accepts requests via HTTP (the network protocol created to distribute web content) or its secure variant HTTPS. A user agent, commonly a web browser or web crawler, initiate ...s), published in July since 2003. References External links * * Archives , https://www.ncbi.nlm.nih.gov/pmc/journals/4/ Biochemistry journals Open access j ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antibiotics
An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting bacterial infections, and antibiotic medications are widely used in the treatment and prevention of such infections. They may either kill or inhibit the growth of bacteria. A limited number of antibiotics also possess antiprotozoal activity. Antibiotics are not effective against viruses such as the common cold or influenza; drugs which inhibit viruses are termed antiviral drugs or antivirals rather than antibiotics. Sometimes, the term ''antibiotic''—literally "opposing life", from the Greek roots ἀντι ''anti'', "against" and βίος ''bios'', "life"—is broadly used to refer to any substance used against microbes, but in the usual medical usage, antibiotics (such as penicillin) are those produced naturally (by one microorganism fighting another), whereas non-antibiotic antibacterials (such as sulfonamides and antisep ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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