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Cell Immobilization Technologies for Applications in Alcoholic Beverages
Published in Munmaya K. Mishra, Applications of Encapsulation and Controlled Release, 2019
Argyro Bekatorou, Stavros Plessas, Athanasios Mallouchos
A large number of studies report the selection or improvement of psychrophilic, psychrotolerant, or cold-adapted yeasts for low-temperature alcoholic beverages or ethanol production, and many more describe the development of low-temperature fermentation processes employing immobilized cell systems. Metabolic and physiological changes in yeast are not only induced in psychrophilic species evolved in cold environments but are also common during growth or fermentation processes at low temperatures. S. cerevisiae is naturally found in environments, such as the surface of fruit, that can be subjected to low temperatures. In alcoholic fermentation processes, these yeasts can be exposed to temperatures around 10 to 12 °C, while industrial strains may be stored at very low temperatures (4 °C), at which viability is maintained but growth is restricted.54 In S. cerevisiae, low temperatures induce the expression of genes that display a cold-sensitivity phenotype, including the induction of fatty acid desaturases, proteins involved in pre-rRNA processing and ribosome biogenesis, specific amino acid–rich cell wall proteins, altered nitrogen metabolism, changes in the membrane fatty acids, alterations in aroma-related biochemical reactions, etc.54
Electron Microscopy Studies of Dynein: From Subdomains to Microtubule-Bound Assemblies
Published in Keiko Hirose, Handbook of Dynein, 2019
Anthony J. Roberts, Katerina Toropova, Hiroshi Imai
Sequence analysis shows that the head contains six AAA+ modules (termed AAA1–AAA6; Fig. 3.1A), placing dynein in the AAA+ superfamily of ATPases [55]. Many AAA+ proteins contain one AAA+ module per polypeptide and assemble into homo-hexameric ring structures, which exert vectorial work by threading a substrate through their axial pore. EM analysis of truncated dynein constructs demonstrated that its six AAA+ modules also form a hexameric ring (Fig. 3.1C). While the ring-like appearance of dynein’s core is consistent with its AAA+ relatives, the fusion of the six AAA+ modules into a single polypeptide is a special feature of the dynein lineage. Only dynein’s closest known relative—midasin, which functions in ribosome biogenesis—appears to share this feature [18, 94].
Plant Responses to Electromagnetic Fields
Published in Ben Greenebaum, Frank Barnes, Biological and Medical Aspects of Electromagnetic Fields, 2018
High-gradient MF has been used to induce intracellular magnetophoresis of amyloplasts and the obtained data indicate that a magnetic force can be used to study the gravisensing and response system of roots (Kuznetsov and Hasenstein, 1996). The data reported strongly support the amyloplast-based gravity-sensing system in higher plants and the usefulness of high MF to substitute gravity in shoots (Kuznetsov and Hasenstein, 1997; Kuznetsov et al., 1999). For example, in shoots of the lazy-2 mutant of tomato that exhibit negative gravitropism in the dark, but respond positively gravitropically in (red) light, induced magnetophoretic curvature showed that lazy-2 mutants perceive the displacement of amyloplasts in a similar manner than wild type and that the high MF does not affect the graviresponse mechanism (Hasenstein and Kuznetsov, 1999). Arabidopsis stems positioned in a high MF on a rotating clinostat demonstrate that the lack of apical curvature after basal amyloplast displacement indicates that gravity perception in the base is not transmitted to the apex (Weise et al., 2000). The movement of corn, wheat, and potato (Solanum tuberosum) starch grains in suspension was examined with videomicroscopy during parabolic flights that generated 20–25 s of weightlessness. During weightlessness, a magnetic gradient was generated by inserting a wedge into a uniform, external MF that caused repulsion of starch grains. Magnetic gradients were able to move diamagnetic compounds under weightless or microgravity conditions and serve as directional stimulus during seed germination in low-gravity environments (Hasenstein et al., 2013). The response of transgenic seedlings of Arabidopsis, containing either the CycB1-GUS proliferation marker or the DR5-GUS auxin-mediated growth marker, to diamagnetic levitation in the bore of a superconducting solenoid magnet was evaluated. Diamagnetic levitation led to changes that are very similar to those caused by real [i.e., on board the International Space Station (ISS)] or mechanically simulated microgravity [i.e., using a random positioning machine (RPM)]. These changes decoupled meristematic cell proliferation from ribosome biogenesis, and altered auxin polar transport (Manzano et al., 2013). Arabidopsis in vitro callus cultures were also exposed to environments with different levels of effective gravity and MF strengths simultaneously. The MF itself produced a low number of proteomic alterations, but the combination of gravitational alteration and MF exposure produced synergistic effects on the proteome of plants (Herranz et al., 2013). However, MF leads to redistribution of the cellular activities and this is why application of the proteomic analysis to the whole organs/plants is not so informative.
It's not just about protein turnover: the role of ribosomal biogenesis and satellite cells in the regulation of skeletal muscle hypertrophy
Published in European Journal of Sport Science, 2019
Matthew Stewart Brook, Daniel James Wilkinson, Ken Smith, Philip James Atherton
As ribosomes serve as the protein synthetic machinery of the cell, the rate of protein synthesis is not only determined by translational efficiency (discussed above) but also the total number of ribosomes (translational capacity) (Millward, Garlick, James, Nnanyelugo, & Ryatt, 1973). Ribosomes are themselves composed of RNA (ribosomal RNA (rRNA)), transcribed by RNA polymerase 1 (POL1) as a 47S pre-rRNA which is then cleaved into 28S, 18S, 5.8S and subsequently assembled with ribonuclear proteins to from a mature ribosome (Figure 1) (Chaillou, Kirby, & Mccarthy, 2014). POL1 therefore serves as a primary control point in ribosomal biogenesis, with the transcription factors TIF-1A, TIF-1B and UBF key in forming a PIC with POL1 at the rDNA promoter. The regulation of TIF-1A and UBF transcriptional activity is achieved through multiple signaling proteins, including ERK, AMPK, mTORc1 and P70S6K1 (reviewed in Kusnadi et al., 2015) enabling the control of ribosomal biogenesis to be influenced by multiple pathways such as hormones, nutrients and contractile activity. Another key regulator of ribosomal biogenesis is c-MYC, an oncoprotein involved in regulating cell growth and virtually all aspects of ribosome formation. c-MYC directly upregulates many of the proteins involved in rDNA transcriptional control including UBF, TIF-1A, TIF-1B, Pol1 and many other proteins involved in the formation, processing and export of mature ribosomes. Further, c-MYC enhances POL1 transcription by remodeling rDNA chromatin structure and directly interacting with the SL1 complex, stabilising Pol1 recruitment at the promoter (van Riggelen, Yetil, & Felsher, 2010). Day-to-day fluctuations in MPS that maintain muscle mass in healthy individuals are predominantly achieved by transient increases in translational efficiency, without changes in RNA content (Chesley et al., 1992). RNA content and therefore ribosome number is likely to be adequately maintained to sustain the protein synthetic needs of habitual activity and nutritional intake, whilst being continually replenished to maintain functional ribosomes. In support of this, ribosomal biogenesis pathways are entwined with those regulating translational efficiency (i.e. mTORc1) (Mayer & Grummt, 2006) (Figure 1) and in response to chronic muscle loading or nutritional modulation, bio-markers of increased ribosomal biogenesis are observed (i.e. Increased c-MYC / 47s pre-RNA) (Stec, Mayhew, & Bamman, 2015).