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KaiABC
In molecular biology, the cyanobacterial clock proteins are the main circadian regulator in cyanobacteria. The cyanobacterial clock proteins comprise three proteins: KaiA, KaiB and KaiC. The kaiABC Protein complex, complex may act as a Promoter (genetics), promoter-nonspecific Transcriptional regulation, transcription regulator that represses Transcription (genetics), transcription, possibly by acting on the state of chromosome compaction. This complex is expressed from a ''KaiABC'' operon. See also: bacterial circadian rhythms In the complex, KaiA enhances the phosphorylation status of kaiC. In contrast, the presence of kaiB in the complex decreases the phosphorylation status of kaiC, suggesting that kaiB acts by antagonising the interaction between kaiA and kaiC. The activity of KaiA activates kaiBC expression, while KaiC represses it. Also in the KaiC family is RadA/Sms, a highly conserved eubacterial protein that shares sequence (biology), sequence similarity with both Rec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
KaiC
KaiC is a gene belonging to the KaiABC gene cluster (with KaiA, and KaiB) that, together, regulate bacterial circadian rhythms, specifically in cyanobacteria. KaiC encodes for the KaiC protein, which interacts with the KaiA and KaiB proteins in a post-translational oscillator (PTO). The PTO is cyanobacteria master clock that is controlled by sequences of phosphorylation of KaiC protein. Regulation of KaiABC expression and KaiABC phosphorylation is essential for cyanobacteria circadian rhythmicity, and is particularly important for regulating cyanobacteria processes such as nitrogen fixation, photosynthesis, and cell division. Studies have shown similarities to Drosophila, Neurospora, and mammalian clock models in that the kaiABC regulation of the cyanobacteria slave circadian clock is also based on a transcription translation feedback loop (TTFL). KaiC protein has both auto-kinase and auto-phosphatase activity and functions as the circadian regulator in both the PTO and the TTFL ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bacterial Circadian Rhythms
Bacterial circadian rhythms, like other circadian rhythms, are endogenous "biological clocks" that have the following three characteristics: (a) in constant conditions (i.e. constant temperature and either constant light or constant darkness ) they oscillate with a period that is close to, but not exactly, 24 hours in duration, (b) this " free-running" rhythm is temperature compensated, and (c) the rhythm will entrain to an appropriate environmental cycle. Until the mid-1980s, it was thought that only eukaryotic cells had circadian rhythms. It is now known that cyanobacteria (a phylum of photosynthetic eubacteria) have well-documented circadian rhythms that meet all the criteria of bona fide circadian rhythms. In these bacteria, three key proteins whose structures have been determined can form a molecular clockwork that orchestrates global gene expression. This system enhances the fitness of cyanobacteria in rhythmic environments. History: are prokaryotes capable of circadian rhyt ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Circadian
A circadian rhythm (), or circadian cycle, is a natural, internal process that regulates the sleep–wake cycle and repeats roughly every 24 hours. It can refer to any process that originates within an organism (i.e., endogenous) and responds to the environment ( entrained by the environment). These 24-hour rhythms are driven by a circadian clock, and they have been widely observed in animals, plants, fungi and cyanobacteria. The term ''circadian'' comes from the Latin ''circa'', meaning "approximately", and ''dies'', meaning "day". Processes with 24-hour cycles are more generally called diurnal rhythms; diurnal rhythms should not be called circadian rhythms unless they can be confirmed as endogenous, and not environmental. Although circadian rhythms are endogenous, they are adjusted to the local environment by external cues called zeitgebers (German for "time givers"), which include light, temperature and redox cycles. In clinical settings, an abnormal circadian rhythm in humans ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Peptide
Peptides (, ) are short chains of amino acids linked by peptide bonds. Long chains of amino acids are called proteins. Chains of fewer than twenty amino acids are called oligopeptides, and include dipeptides, tripeptides, and tetrapeptides. A polypeptide is a longer, continuous, unbranched peptide chain. Hence, peptides fall under the broad chemical classes of biological polymers and oligomers, alongside nucleic acids, oligosaccharides, polysaccharides, and others. A polypeptide that contains more than approximately 50 amino acids is known as a protein. Proteins consist of one or more polypeptides arranged in a biologically functional way, often bound to ligands such as coenzymes and cofactors, or to another protein or other macromolecule such as DNA or RNA, or to complex macromolecular assemblies. Amino acids that have been incorporated into peptides are termed residues. A water molecule is released during formation of each amide bond.. All peptides except cyclic pep ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Homodimer
In biochemistry, a protein dimer is a macromolecular complex formed by two protein monomers, or single proteins, which are usually non-covalently bound. Many macromolecules, such as proteins or nucleic acids, form dimers. The word ''dimer'' has roots meaning "two parts", '' di-'' + '' -mer''. A protein dimer is a type of protein quaternary structure. A protein homodimer is formed by two identical proteins. A protein heterodimer is formed by two different proteins. Most protein dimers in biochemistry are not connected by covalent bonds. An example of a non-covalent heterodimer is the enzyme reverse transcriptase, which is composed of two different amino acid chains. An exception is dimers that are linked by disulfide bridges such as the homodimeric protein NEMO. Some proteins contain specialized domains to ensure dimerization (dimerization domains) and specificity. The G protein-coupled cannabinoid receptors have the ability to form both homo- and heterodimers with several ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Secondary Structure
Protein secondary structure is the three dimensional conformational isomerism, form of ''local segments'' of proteins. The two most common Protein structure#Secondary structure, secondary structural elements are alpha helix, alpha helices and beta sheets, though beta turns and omega loops occur as well. Secondary structure elements typically spontaneously form as an intermediate before the protein protein folding, folds into its three dimensional protein tertiary structure, tertiary structure. Secondary structure is formally defined by the pattern of hydrogen bonds between the Amine, amino hydrogen and carboxyl oxygen atoms in the peptide backbone chain, backbone. Secondary structure may alternatively be defined based on the regular pattern of backbone Dihedral angle#Dihedral angles of proteins, dihedral angles in a particular region of the Ramachandran plot regardless of whether it has the correct hydrogen bonds. The concept of secondary structure was first introduced by Kaj Ulrik ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protein Dimer
In biochemistry, a protein dimer is a macromolecular complex formed by two protein monomers, or single proteins, which are usually non-covalently bound. Many macromolecules, such as proteins or nucleic acids, form dimers. The word ''dimer'' has roots meaning "two parts", '' di-'' + '' -mer''. A protein dimer is a type of protein quaternary structure. A protein homodimer is formed by two identical proteins. A protein heterodimer is formed by two different proteins. Most protein dimers in biochemistry are not connected by covalent bonds. An example of a non-covalent heterodimer is the enzyme reverse transcriptase, which is composed of two different amino acid chains. An exception is dimers that are linked by disulfide bridges such as the homodimeric protein NEMO. Some proteins contain specialized domains to ensure dimerization (dimerization domains) and specificity. The G protein-coupled cannabinoid receptors have the ability to form both homo- and heterodimers with several ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alpha Helix
The alpha helix (α-helix) is a common motif in the secondary structure of proteins and is a right hand-helix conformation in which every backbone N−H group hydrogen bonds to the backbone C=O group of the amino acid located four residues earlier along the protein sequence. The alpha helix is also called a classic Pauling–Corey–Branson α-helix. The name 3.613-helix is also used for this type of helix, denoting the average number of residues per helical turn, with 13 atoms being involved in the ring formed by the hydrogen bond. Among types of local structure in proteins, the α-helix is the most extreme and the most predictable from sequence, as well as the most prevalent. Discovery In the early 1930s, William Astbury showed that there were drastic changes in the X-ray fiber diffraction of moist wool or hair fibers upon significant stretching. The data suggested that the unstretched fibers had a coiled molecular structure with a characteristic repeat of ≈. Astb ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Monomer
In chemistry, a monomer ( ; ''mono-'', "one" + '' -mer'', "part") is a molecule that can react together with other monomer molecules to form a larger polymer chain or three-dimensional network in a process called polymerization. Classification Monomers can be classified in many ways. They can be subdivided into two broad classes, depending on the kind of the polymer that they form. Monomers that participate in condensation polymerization have a different stoichiometry than monomers that participate in addition polymerization: : Other classifications include: *natural vs synthetic monomers, e.g. glycine vs caprolactam, respectively *polar vs nonpolar monomers, e.g. vinyl acetate vs ethylene, respectively *cyclic vs linear, e.g. ethylene oxide vs ethylene glycol, respectively The polymerization of one kind of monomer gives a homopolymer. Many polymers are copolymers, meaning that they are derived from two different monomers. In the case of condensation polymerizations, the r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protein Folding
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] |
Genetic Redundancy
{{short description, Biological situation Genetic redundancy is a term typically used to describe situations where a given biochemical function is redundantly encoded by two or more genes. In these cases, mutations (or defects) in one of these genes will have a smaller effect on the fitness of the organism than expected from the genes’ function. Characteristic examples of genetic redundancy include (Enns, Kanaoka et al. 2005) and (Pearce, Senis et al. 2004). Many more examples are thoroughly discussed in (Kafri, Levy & Pilpel. 2006). The main source of genetic redundancy is the process of gene duplication which generates multiplicity in gene copy number. A second and less frequent source of genetic redundancy are convergent evolutionary processes leading to genes that are close in function but unrelated in sequence (Galperin, Walker & Koonin 1998). Genetic redundancy is typically associated with signaling networks, in which many proteins act together to accomplish teleological func ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Replication Fork
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] |
