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DnaA
Introduction Based on the Replicon Model, a positively active initiator molecule contacts with a particular spot on a circular chromosome called the replicator to start DNA replication. DnaA is a protein that activates initiation of DNA replication in bacteria. It is a replication initiation factor which promotes the unwinding of DNA at oriC. The DnaA proteins found in all bacteria engage with the DnaA boxes to start chromosomal replication. In addition to the DnaA protein, its concentration, binding to DnaA-boxes, and binding of ATP or ADP, we will cover the regulation of the DnaA gene, the unique characteristics of the DnaA gene expression, promoter strength, and translation efficiency. The onset of the initiation phase of DNA replication is determined by the concentration of DnaA. DnaA accumulates during growth and then triggers the initiation of replication. Replication begins with active DnaA binding to 9-mer (9-bp) repeats upstream of oriC. Binding of DnaA leads to strand s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DnaC
dnaC is a loading factor that complexes with the C-terminus of helicase dnaB and inhibits it from unwinding the dsDNA at a replication fork. A dnaB and dnaC associate near the dnaA bound origin for each of the ssDNA. One dnaB-dnaC complex is oriented in the opposite direction to the other dnaB-dnaC complex due to the antiparallel nature of DNA. Because they are oriented in opposite directions, one dnaB-dnaC complex will complex with dnaA from the N-terminus of dnaB whereas the other dnaB-dnaC complex will complex with dnaA from the dnaC. After the assembly of dnaG onto the N-terminus of dnaB, dnaC is released and dnaB will be allowed to begin unwinding dsDNA to make room for DNA polymerase III to begin synthesizing the daughter strands. This interaction of dnaC with dnaB requires the hydrolysis of ATP ATP may refer to: Companies and organizations * Association of Tennis Professionals, men's professional tennis governing body * American Technical Publishers, employee-owned ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DnaB Helicase
DnaB helicase is an enzyme in bacteria which opens the replication fork during DNA replication. Although the mechanism by which DnaB both couples ATP hydrolysis to translocation along DNA and denatures the duplex is unknown, a change in the quaternary structure of the protein involving dimerisation of the N-terminal domain has been observed and may occur during the enzymatic cycle. Initially when DnaB binds to dnaA, it is associated with dnaC, a negative regulator. After DnaC dissociates, DnaB binds dnaG. The N-terminal has a multi-helical structure that forms an orthogonal bundle. The C-terminal domain contains an ATP-binding site and is therefore probably the site of ATP hydrolysis. In eukaryotes, helicase function is provided by the MCM ( Minichromosome maintenance) complex. The DnaB helicase is the product of the ''dnaB'' gene. The helicase enzyme that is produced is a hexamer in ''E. coli'', as well as in many other bacteria. The energy for DnaB activity is provide ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DnaN
dnaN is the gene that codes for the DNA clamp (also known as β sliding clamp) of DNA polymerase III in prokaryotes. The β clamp physically locks Pol III onto a DNA strand during replication to help increase its processivity. The eukaryotic equivalent to the β clamp is PCNA Proliferating cell nuclear antigen (PCNA) is a DNA clamp that acts as a processivity factor for DNA polymerase δ in eukaryotic cells and is essential for replication. PCNA is a homotrimer and achieves its processivity by encircling the DNA, .... See also * Beta clamp References DNA replication {{molecular-biology-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Escherichia Coli
''Escherichia coli'' (),Wells, J. C. (2000) Longman Pronunciation Dictionary. Harlow ngland Pearson Education Ltd. also known as ''E. coli'' (), is a Gram-negative, facultative anaerobic, rod-shaped, coliform bacterium of the genus '' Escherichia'' that is commonly found in the lower intestine of warm-blooded organisms. Most ''E. coli'' strains are harmless, but some serotypes ( EPEC, ETEC etc.) can cause serious food poisoning in their hosts, and are occasionally responsible for food contamination incidents that prompt product recalls. Most strains do not cause disease in humans and are part of the normal microbiota of the gut; such strains are harmless or even beneficial to humans (although these strains tend to be less studied than the pathogenic ones). For example, some strains of ''E. coli'' benefit their hosts by producing vitamin K2 or by preventing the colonization of the intestine by pathogenic bacteria. These mutually beneficial relationships between ''E. co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DnaG
DnaG is a bacterial DNA primase and is encoded by the ''dnaG'' gene. The enzyme DnaG, and any other DNA primase, synthesizes short strands of RNA known as oligonucleotides during DNA replication. These oligonucleotides are known as primers because they act as a starting point for DNA synthesis. DnaG catalyzes the synthesis of oligonucleotides that are 10 to 60 nucleotides (the fundamental unit of DNA and RNA) long, however most of the oligonucleotides synthesized are 11 nucleotides. These RNA oligonucleotides serve as primers, or starting points, for DNA synthesis by bacterial DNA polymerase III (Pol III). DnaG is important in bacterial DNA replication because DNA polymerase cannot initiate the synthesis of a DNA strand, but can only add nucleotides to a preexisting strand. DnaG synthesizes a single RNA primer at the origin of replication. This primer serves to prime leading strand DNA synthesis. For the other parental strand, the lagging strand, DnaG synthesizes an RNA prime ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
RIDA
Rida ( ar, رضا, ''Riḍā'') is an Arabic name, "''riḍā''" literally means 'Veil '. In religious context, this term is interpreted as ''satisfaction'' or "''perfect contentment'' with God's will or decree". It is neutral Arabic name, given as first name by Arab and Muslim communities of all sects, as well as in the Arab Christian community, and in the Druze community. Within Islam ''Riḍā'' is often found rather vaguely within the English translation of the Qur'an, and in the life accounts of Sufi saints such as Rābiʻa al-ʻAdawiyya al-Qaysiyya (Rabia al-Adawiyya). According to Annemarie Schimmel, author of ''Mystical Dimensions of Islam'', "riḍā is closely related to shukr, or gratitude", another virtue within Islam. Other possible related virtues would be sabr, faqr, tawakkul, and zuhd; all coalescing to form "perfect sincerity" or ''ikhlas''. Within the Qur'an The following are some examples of possible interpretations of ''riḍā'' within the Qur'an: *"(All) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Autoregulation
Autoregulation is a process within many biological systems, resulting from an internal adaptive mechanism that works to adjust (or mitigate) that system's response to stimuli. While most systems of the body show some degree of autoregulation, it is most clearly observed in the kidney, the heart, and the brain. Perfusion of these organs is essential for life, and through autoregulation the body can divert blood (and thus, oxygen) where it is most needed. Cerebral autoregulation More so than most other organs, the brain is very sensitive to increased or decreased blood flow, and several mechanisms (metabolic, myogenic, and neurogenic) are involved in maintaining an appropriate cerebral blood pressure. Brain blood flow autoregulation is abolished in several disease states such as traumatic brain injury, stroke, brain tumors, or persistent abnormally high levels. Homeometrics and heterometric autoregulation of the heart Homeometric autoregulation, in the context of the circulator ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transcription (biology)
Transcription is the process of copying a segment of DNA into RNA. The segments of DNA transcribed into RNA molecules that can encode proteins are said to produce messenger RNA (mRNA). Other segments of DNA are copied into RNA molecules called non-coding RNAs (ncRNAs). mRNA comprises only 1–3% of total RNA samples. Less than 2% of the human genome can be transcribed into mRNA ( Human genome#Coding vs. noncoding DNA), while at least 80% of mammalian genomic DNA can be actively transcribed (in one or more types of cells), with the majority of this 80% considered to be ncRNA. Both DNA and RNA are nucleic acids, which use base pairs of nucleotides as a complementary language. During transcription, a DNA sequence is read by an RNA polymerase, which produces a complementary, antiparallel RNA strand called a primary transcript. Transcription proceeds in the following general steps: # RNA polymerase, together with one or more general transcription factors, binds to promoter ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
RNA Polymerase
In molecular biology, RNA polymerase (abbreviated RNAP or RNApol), or more specifically DNA-directed/dependent RNA polymerase (DdRP), is an enzyme that synthesizes RNA from a DNA template. Using the enzyme helicase, RNAP locally opens the double-stranded DNA so that one strand of the exposed nucleotides can be used as a template for the synthesis of RNA, a process called transcription. A transcription factor and its associated transcription mediator complex must be attached to a DNA binding site called a promoter region before RNAP can initiate the DNA unwinding at that position. RNAP not only initiates RNA transcription, it also guides the nucleotides into position, facilitates attachment and elongation, has intrinsic proofreading and replacement capabilities, and termination recognition capability. In eukaryotes, RNAP can build chains as long as 2.4 million nucleotides. RNAP produces RNA that, functionally, is either for protein coding, i.e. messenger RNA (mRNA); ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Promoter (genetics)
In genetics, a promoter is a sequence of DNA to which proteins bind to initiate transcription of a single RNA transcript from the DNA downstream of the promoter. The RNA transcript may encode a protein (mRNA), or can have a function in and of itself, such as tRNA or rRNA. Promoters are located near the transcription start sites of genes, upstream on the DNA (towards the 5' region of the sense strand). Promoters can be about 100–1000 base pairs long, the sequence of which is highly dependent on the gene and product of transcription, type or class of RNA polymerase recruited to the site, and species of organism. Promoters control gene expression in bacteria and eukaryotes. RNA polymerase must attach to DNA near a gene for transcription to occur. Promoter DNA sequences provide an enzyme binding site. The -10 sequence is TATAAT. -35 sequences are conserved on average, but not in most promoters. Artificial promoters with conserved -10 and -35 elements transcribe more slowly. All ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Conserved Sequence
In evolutionary biology, conserved sequences are identical or similar sequences in nucleic acids ( DNA and RNA) or proteins across species ( orthologous sequences), or within a genome ( paralogous sequences), or between donor and receptor taxa ( xenologous sequences). Conservation indicates that a sequence has been maintained by natural selection. A highly conserved sequence is one that has remained relatively unchanged far back up the phylogenetic tree, and hence far back in geological time. Examples of highly conserved sequences include the RNA components of ribosomes present in all domain (biology), domains of life, the homeobox sequences widespread amongst Eukaryotes, and the tmRNA in Bacteria. The study of sequence conservation overlaps with the fields of genomics, proteomics, evolutionary biology, phylogenetics, bioinformatics and mathematics. History The discovery of the role of DNA#History, DNA in heredity, and observations by Frederick Sanger of variation betwee ... [...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-conservativ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
