Amino Acids, Essential
Hemorrhagic Fever, American
Oceanic Ancestry Group
Phosphocarrier proteins in an intracellular symbiotic bacterium of aphids. (1/120)A GroEL homolog produced by Buchnera, an intracellular symbiotic bacterium of aphids, is not only a molecular chaperone but also a novel phosphocarrier protein, suggesting that this protein plays a role in a signal transducing system specific to bacteria living in an intracellular environment. This prompted us to look into phosphocarrier proteins of Buchnera that may be shared in common with other bacteria. As a result, no evidence was obtained for the presence of sensor kinases of the two-component system in Buchnera, which are found in many bacteria. It is possible that the lack of sensor kinases is compensated for by the mulitifunctional GroEL homolog in this symbiotic bacteria. In contrast, we successfully identified three phosphotransferase system genes, ptsH, ptsI, and crr in Buchnera, and provide evidence for their active expression. While the deduced amino acid sequences of these gene products, histidine-containing phosphocarrier protein, Enzyme I, and Enzyme III were similar to their counterparts in Escherichia coli, the predicted isoelectric points of the Buchnera proteins were strikingly higher. It was also suggested that Buchnera Enzyme I, when produced in E. coli, is able to accept the phosphoryl group from phosphoenolpyruvate, but not from ATP. (+info)
Sequence evolution in bacterial endosymbionts having extreme base compositions. (2/120)A major limitation on ability to reconstruct bacterial evolution is the lack of dated ancestors that might be used to evaluate and calibrate molecular clocks. Vertically transmitted symbionts that have cospeciated with animal hosts offer a firm basis for calibrating sequence evolution in bacteria, since fossils of the hosts can be used to date divergence events. Sequences for a functionally diverse set of genes have been obtained for bacterial endosymbionts (Buchnera) from two pairs of aphid host species, each pair diverging 50-70 MYA. Using these dates and estimated numbers of Buchnera generations per year, we calculated rates of base substitution for neutral and selected sites of protein-coding genes and overall rates for rRNA genes. Buchnera shows homogeneity among loci with regard to synonymous rate. The Buchnera synonymous rate is about twice that for low-codon-bias genes of Escherichia coli-Salmonella typhimurium on an absolute timescale, and fourfold higher on a generational timescale. Nonsynonymous substitutions show a greater rate disparity in favor of Buchnera, a result consistent with a genomewide decrease in selection efficiency in Buchnera. Ratios of synonymous to nonsynonymous substitutions differ for the two pairs of Buchnera, indicating that selection efficiency varies among lineages. Like numerous other intracellular bacteria, such as Rickettsia and Wolbachia, Buchnera has accumulated amino acids with codons rich in A or T. Phylogenetic reconstruction of amino acid replacements indicates that replacements yielding increased A + T predominated early in the evolution of Buchnera, with the trend slowing or stopping during the last 50 Myr. This suggests that base composition in Buchnera has approached a limit enforced by selective constraint acting on protein function. (+info)
Identifying the determinants in the equatorial domain of Buchnera GroEL implicated in binding Potato leafroll virus. (3/120)Luteoviruses avoid degradation in the hemolymph of their aphid vector by interacting with a GroEL homolog from the aphid's primary endosymbiotic bacterium (Buchnera sp.). Mutational analysis of GroEL from the primary endosymbiont of Myzus persicae (MpB GroEL) revealed that the amino acids mediating binding of Potato leafroll virus (PLRV; Luteoviridae) are located within residues 9 to 19 and 427 to 457 of the N-terminal and C-terminal regions, respectively, of the discontinuous equatorial domain. Virus overlay assays with a series of overlapping synthetic decameric peptides and their derivatives demonstrated that R13, K15, L17, and R18 of the N-terminal region and R441 and R445 of the C-terminal region of the equatorial domain of GroEL are critical for PLRV binding. Replacement of R441 and R445 by alanine in full-length MpB GroEL and in MpB GroEL deletion mutants reduced but did not abolish PLRV binding. Alanine substitution of either R13 or K15 eliminated the PLRV-binding capacity of the other and those of L17 and R18. In the predicted tertiary structure of GroEL, the determinants mediating virus binding are juxtaposed in the equatorial plain. (+info)
Prephenate dehydratase from the aphid endosymbiont (Buchnera) displays changes in the regulatory domain that suggest its desensitization to inhibition by phenylalanine. (4/120)Buchnera aphidicola, the prokaryotic endosymbiont of aphids, complements dietary deficiencies with the synthesis and provision of several essential amino acids. We have cloned and sequenced a region of the genome of B. aphidicola isolated from Acyrthosiphon pisum which includes the two-domain aroQ/pheA gene. This gene encodes the bifunctional chorismate mutase-prephenate dehydratase protein, which plays a central role in L-phenylalanine biosynthesis. Two changes involved in the overproduction of this amino acid have been detected. First, the absence of an attenuator region suggests a constitutive expression of this gene. Second, the regulatory domain of the Buchnera prephenate dehydratase shows changes in the ESRP sequence, which is involved in the allosteric binding of phenylalanine and is strongly conserved in prephenate dehydratase proteins from practically all known organisms. These changes suggest the desensitization of the enzyme to inhibition by phenylalanine and would permit the bacterial endosymbiont to overproduce phenylalanine. (+info)
Decoupling of genome size and sequence divergence in a symbiotic bacterium. (5/120)In contrast to genome size variation in most bacterial taxa, the small genome size of Buchnera sp. was shown to be highly conserved across genetically diverse isolates (630 to 643 kb). This exceptional size conservation may reflect the inability of this obligate mutualist to acquire foreign DNA and reduced selection for genetic novelty within a static intracellular environment. (+info)
Polyamine composition and expression of genes related to polyamine biosynthesis in an aphid endosymbiont, Buchnera. (6/120)Polyamine composition in an aphid endosymbiotic bacterium, Buchnera sp., was determined by high-performance liquid chromatographic analysis. We found that Buchnera contained virtually only a single polyamine, spermidine. The spermidine content of Buchnera was considerably higher in young aphids and tended to decrease with the age of the host. Expression of speD and speE, whose gene products are key enzymes in the synthesis of spermidine, was analyzed by real-time quantitative reverse transcription-PCR. It was shown that the levels of their mRNAs fluctuated in line with the spermidine content. (+info)
Decay of mutualistic potential in aphid endosymbionts through silencing of biosynthetic loci: Buchnera of Diuraphis. (7/120)Buchnera, the primary bacterial endosymbiont of aphids, is known to provision essential amino acids lacking in the hosts' diet of plant sap. The recent discovery of silenced copies of genes for tryptophan biosynthesis (trpEG) in certain Buchnera lineages suggests a decay in symbiotic functions in some aphid species. However, neither the distribution of pseudogenes among lineages nor the impact of this gene silencing on amino-acid availability in hosts has been assessed. In Buchnera of the aphid Diuraphis noxia, tandem repeats of these pseudogenes have persisted in diverse lineages, and thpEG pseudogenes have originated at least twice within this aphid genus. Measures of amino-acid concentrations in Diuraphis species have shown that the presence of the pseudogene is associated with a decreased availability of tryptophan, indicating that gene silencing decreases nutrient provisioning by symbionts. In Buchnera of Diuraphis, rates of nonsynonymous substitutions are elevated in functional trpE copies, supporting the hypothesis that pseudogene origin and persistence reflect a reduced selection for symbiont biosynthetic contributions. The parallel evolution of trpEG pseudogenes in Buchnera of Diuraphis and certain other aphid hosts suggests that either selection at the host level is not effective or that fitness in these aphids is not limited by tryptophan availability. (+info)
Postsymbiotic plasmid acquisition and evolution of the repA1-replicon in Buchnera aphidicola. (8/120)Buchnera aphidicola is an obligate, strictly vertically transmitted, bacterial symbiont of aphids. It supplies its host with essential amino acids, nutrients required by aphids but deficient in their diet of plant phloem sap. Several lineages of Buchnera show adaptation to their nutritional role in the form of plasmid-mediated amplification of key-genes involved in the biosynthesis of tryptophan (trpEG) and leucine (leuABCD). Phylogenetic analyses of these plasmid-encoded functions have thus far suggested the absence of horizontal plasmid exchange among lineages of Buchnera. Here, we describe three new Buchnera plasmids, obtained from species of the aphid host families Lachnidae and Pemphigidae. All three plasmids belong to the repA1 family of Buchnera plasmids, which is characterized by the presence of a repA1-replicon responsible for replication initiation. A comprehensive analysis of this family of plasmids unexpectedly revealed significantly incongruent phylogenies for different plasmid and chromosomally encoded loci. We infer from these incongruencies a case of horizontal plasmid transfer in Buchnera. This process may have been mediated by secondary endosymbionts, which occasionally undergo horizontal transmission in aphids. (+info)
Anthranilate synthase is an enzyme that plays a key role in the biosynthesis of the amino acid tryptophan in plants, fungi, and some bacteria. It catalyzes the conversion of chorismate, a precursor molecule, into anthranilate, which is a key intermediate in the tryptophan biosynthesis pathway. In the medical field, anthranilate synthase has been studied as a potential target for the development of new antibiotics and herbicides. For example, some bacteria that are resistant to conventional antibiotics have been found to produce anthranilate synthase enzymes that are different from those found in susceptible bacteria. This has led to the development of new antibiotics that target these enzymes. In addition, anthranilate synthase has been studied as a potential target for the development of herbicides that selectively kill certain plant species. This is because the enzyme is not present in all plant species, and its inhibition can lead to the death of specific plants without harming other crops or non-target organisms. Overall, anthranilate synthase is an important enzyme in the biosynthesis of tryptophan and has potential applications in the development of new antibiotics and herbicides.
In the medical field, "Amino Acids, Essential" refers to a group of nine amino acids that cannot be synthesized by the human body and must be obtained through the diet. These amino acids are essential for the growth and maintenance of tissues, as well as for the production of hormones and enzymes. They are considered "essential" because the body cannot produce them on its own and must obtain them from food sources. The nine essential amino acids are: isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine, and histidine.
Chaperonin 60, also known as GroEL or Hsp60, is a protein complex that plays a crucial role in the folding and assembly of proteins in the cell. It is found in all organisms, from bacteria to humans, and is particularly important in the folding of newly synthesized proteins and the refolding of misfolded proteins. The chaperonin 60 complex consists of two identical subunits, each with a molecular weight of approximately 60 kDa, hence the name. The subunits form a barrel-like structure with a central cavity that can accommodate unfolded or partially folded proteins. The complex uses energy from ATP hydrolysis to facilitate the folding process by stabilizing the intermediate states of the protein as it folds into its final structure. In the medical field, chaperonin 60 has been implicated in a number of diseases, including neurodegenerative disorders such as Alzheimer's and Parkinson's disease, as well as certain types of cancer. Abnormal folding of chaperonin 60 has also been linked to the development of certain types of bacterial infections. As such, understanding the role of chaperonin 60 in protein folding and its involvement in disease may lead to the development of new therapeutic strategies for these conditions.
Hemifacial spasm is a neurological disorder characterized by involuntary and repetitive contractions of the muscles on one side of the face. The spasms can range from mild to severe and can cause the affected person to blink, smile, or frown involuntarily. The spasms can also cause the face to twist or jerk, which can be embarrassing and affect a person's quality of life. Hemifacial spasm is caused by damage to the facial nerve, which controls the muscles of the face. The damage can be due to a variety of factors, including compression of the nerve by a blood vessel, injury to the nerve, or a tumor. Treatment for hemifacial spasm may include medications, botulinum toxin injections, or surgery.
Hemorrhagic Fever, American (also known as American Hemorrhagic Fever or AHF) is a rare and potentially deadly viral disease caused by the Lassa virus. It is primarily found in West Africa, particularly in Nigeria, Liberia, Sierra Leone, and Guinea, but cases have also been reported in other parts of the world where travelers or healthcare workers have been exposed to the virus. AHF is transmitted to humans through contact with the urine, feces, or respiratory secretions of infected rodents, particularly the multimammate rat (Mastomys natalensis). The virus can also be transmitted through contact with contaminated objects or surfaces. Symptoms of AHF typically include fever, headache, muscle aches, weakness, and fatigue. In severe cases, the disease can progress to bleeding from the nose, mouth, and other mucous membranes, as well as internal bleeding, which can be life-threatening. There is no specific treatment for AHF, and supportive care is the mainstay of therapy. Vaccines are available to prevent Lassa fever, but they are not widely available and are not effective against all strains of the virus. Therefore, the best way to prevent AHF is to avoid contact with infected rodents and their excreta, and to practice good hygiene and sanitation.
Protein Tyrosine Phosphatases, Non-Receptor (PTPNs) are a family of enzymes that play a crucial role in regulating cellular signaling pathways by removing phosphate groups from tyrosine residues on proteins. These enzymes are involved in a wide range of cellular processes, including cell growth, differentiation, migration, and apoptosis. PTPNs are characterized by their ability to hydrolyze the phospho-tyrosine bond on specific target proteins, leading to the dephosphorylation of these proteins and the modulation of their activity. This process is essential for maintaining the proper balance of signaling pathways in the cell and for regulating the activity of various signaling molecules, such as receptor tyrosine kinases, G-protein coupled receptors, and transcription factors. PTPNs are encoded by a large family of genes, and their activity is regulated by various mechanisms, including post-translational modifications, protein-protein interactions, and subcellular localization. Dysregulation of PTPNs has been implicated in a variety of diseases, including cancer, diabetes, and neurological disorders.