Molecular Organization of Entamoeba Histolytica
Roberto R. Kretschmer in Amebiasis: Infection and Disease by Entamoeba histolytica, 2020
Actively moving amebas do not show anisotropic filaments when studied with polarized microscopy or when stained by specific anti-actin antibodies. Nor is actin seen in filamentous form when phalloidin, a specific compound that binds to structured actin, is used. However, actin is present in the trophozoites, organized in diverse forms and actively participating in motility related processes. Actin was first identified in amebas using specific antibodies55,56 and was later isolated from E. histolytica HM1 cell extracts.57,58 The characterization of this abundant protein showed that it lacks the property of binding to and inhibiting DNAse I, a characteristic of all other eukaryotic actins that have been isolated. Purified amebic actin can be induced to polymerize into 7 nm filaments that are decorated with heavy meromyosin. In vivo, actin appears diffused in the cytoplasm, or in the form of aggregates in the leading pseudopod of actively moving amebas. In cells fixed at 37°C actin can be found organized in endocytic invaginations.36 Bailey et al.59,60 described the induction of actin phagocytic mouths at contact sites by challenging trophozoites with red blood cells, red blood cell ghosts or liposomes. Actin can be induced to form “adhesion plates” by contact of trophozoites with fibronectin or laminin-coated surfaces.36,61
Homology of Nonrepeated DNA Sequences in Phylogeny of Fungal Species
S. K. Dutta in DNA Systematics, 2019
This is probably one of the major sources of evolution of new genes. If a duplicate copy of a gene mutation can accumulate in one gene, the unaltered copy can maintain the original function of the gene. In time, the mutated gene provides the new activity of the modified gene. Among the genes that have been thought to arise in this way is one of the two actin genes in the sea urchin Strongylocentrotus franciscanus. These genes are physically linked and separated by about 5 kb. The two genes are extremely similar (they differ by only 1.7% of nucleotides in the coding region),39 The number of actin genes in fungi are variable. The yeast Saccharomyces cerevisiae has a single actin gene,40,41 while Physarum polycephalum contain 4,42 and Dictyostelium discoideum43,44 has 17. The 17 actin genes of Dictyostelium have been shown to contain transcribed and nontranscribed regions. The coding sequences show a large number of nucleotide differences but few amino acid changes. In the nontranscribed regions, the first 45 nucleotides in the 3′ ends have substantial homology. This indicates that different families of actin genes arose by duplication of the progenitor gene. The conservation of the first 45 nucleotides of the 3′ untranslated region could be due to selective pressure acting to maintain these sequences in evolution.43
Energy Demand of Muscle Machines
Peter W. Hochachka in Muscles as Molecular and Metabolic Machines, 2019
The above discussion suggests that while the contractile unit shows many standard features, its molecular composition shows a great deal of fiber-type specificity. Fast muscle fibers, for example, consist of (i) fast-type myosin (high ATPase), (ii) general muscle type actin, (iii) a- and ß-type tropomyosin, and (iv) fast-type troponins I and T, and C., with the C-isoform displaying 2 Ca++ binding sites per troponin C molecule. Slow-type fibers contain (i) slow-type myosin (derived from gene activation only after either neonatal or fast myosin genes are turned off), (ii) general skeletal muscle type actin, (iii) β-, γ-, and δ-type tropomyosin, (iv) slow-type troponins I and T, and (v) slow-type troponin C (displaying only 1 Ca++ per troponin C molecule). In other words, the isoforms of the contractile machinery are linked in fiber-specific patterns, which correlate with functional specializations. Interestingly, this principle of cooccurrence of fiber-specific contractile components appears to extend to the excitation-contractile coupling phase in the overall process of muscle work.
The effect of natural biomolecules on yttrium oxide nanoparticles from a Daphnia magna survival rate perspective
Published in Nanotoxicology, 2023
Egle Kelpsiene, Tingru Chang, Alexander Khort, Katja Bernfur, Inger Odnevall, Tommy Cedervall, Jing Hua
Vitellogenin-1 has previously been identified as one of the general proteins that bind to NPs after incubation with D. magna. Examples of such NPs include Au NPs (Mattsson et al. 2018), differently surface-charged polystyrene NPs (Kelpsiene et al. 2022), and Ag NPs (Gao et al. 2017). Vitellogenin-1 plays an important role in oogenesis and is highly expressed in females (Hara, Hiramatsu, and Fujita 2016, Gao et al. 2017). Hemoglobin is a polyfunctional molecule that is mainly involved in oxygen binding and transport (Ahmed, Ghatge, and Safo 2020). Serine protease has also been identified to extensively interact with 53 nm sized PS-NH2 NPs and to some extent with 200 nm sized PS-NH2 NPs (Kelpsiene et al. 2022). Our previous findings show that actin, alpha skeletal muscle commonly binds to both negatively and positively charged polystyrene NPs after incubation with D. magna (Kelpsiene et al. 2022). Actin protein plays an important role in the structure and motio of cells. Changes of its expression can lead to toxicity (Gunning et al. 2015). The presence of heat shock 70 kDa protein cognate is in line with previous findings where the protein was reported to be secreted by D. magna in response to metallic NPs (Ellis and Lynch 2020) and to 53 nm sized PS-NH2 NPs (Kelpsiene et al. 2022). Results of this study show lamin-A to only be detected in the 20–40 nm sized Y2O3 NPs sample, the same protein also shown to interact only with the 200 nm sized PS-NH2 NPs (Kelpsiene et al. 2022).
Solanaceae glycoalkaloids: α-solanine and α-chaconine modify the cardioinhibitory activity of verapamil
Published in Pharmaceutical Biology, 2022
Szymon Chowański, Magdalena Winkiel, Monika Szymczak-Cendlak, Paweł Marciniak, Dominika Mańczak, Karolina Walkowiak-Nowicka, Marta Spochacz, Sabino A. Bufo, Laura Scrano, Zbigniew Adamski
Calcium ions are crucial for the contraction of all types of muscles. After influx into the cytoplasm, they interact with myofilaments and ultimately allow for interaction between myosin and actin filaments, and thus for muscle contraction. Since they are a trigger and an executor of muscle contractions, their concentration in the sarcoplasm must be strictly regulated. In striated muscles, cell membrane depolarization is a signal that initiates the cascade responsible for muscle contraction. Changes in the cell membrane potential activate and open the L-type calcium channels. Then, the local increase in Ca2+ concentration activates the ryanodine receptor, a sarcoplasmic calcium channel, which releases the next portion of calcium ions into the cytoplasm, which interacts with myofilaments.
Novel ligands and modulators of triggering receptor expressed on myeloid cells receptor family: 2015-2020 updates
Published in Expert Opinion on Therapeutic Patents, 2021
Harbinder Singh, Vikrant Rai, Sunil K. Nooti, Devendra K. Agrawal
Actin is a family of multi-functional globular proteins present in all eukaryotic cells which has been found to participate in various cellular processes, including muscle contraction, cell division and cytokinesis, cell motility, cell signaling, etc. It was observed that actin could activate the inflammatory response by interacting through TREM-1 [56]. There was a controversy on the presence of actin on the cell surface since actin is a cellular cytoskeleton protein. Besides its presence in the cytoplasm, its distribution was also detected on the surface of platelets in the resting state [57]. Therefore, platelets provide surface actin for TREM-1 recognition to activate signaling. In 2017, Fu et al. found that recombinant actin can directly interact with the recombinant TREM-1 extracellular domain and enhance inflammatory response when injected in wild-type mice but not in TREM-1−/- mice. This amplification of inflammatory response could be inhibited by peptide LP17. It was confirmed that the extracellular actin is co-localized with TREM-1 in the lung tissues of septic mice [56].
Related Knowledge Centers
- Cytoskeleton
- Eukaryote
- Globular Protein
- Microfilament
- Monomer
- Muscle Contraction
- Myofibril
- Protein
- Protein Subunit
- Protein Family