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Structural and Functional Analysis of the Dynein Motor Domain
Published in Keiko Hirose, Handbook of Dynein, 2019
Members of the AAA+ superfamily are engaged in diverse cellular functions, such as membrane fusion, protein degradation, disassembly of protein complexes and DNA replication and recombination [29, 96]. Nevertheless, AAA+ proteins share certain structural characteristics as follows: (1) they have conserved ATP-binding/hydrolysis units of 200–250 amino acids, referred to as AAA+ modules, within their polypeptide chains and (2) they operate as homo- or hetero-oligomers in which typically six AAA+ modules are arranged in a ring-shaped structure [63, 96]. In the case of dynein, six AAA+ modules (AAA1–AAA6) are concatenated in a single polypeptide of the heavy chain [63]. The six AAA+ modules form a ring-like structure, so called AAA+ ring [6, 7, 50, 84, 86]. Amongst AAA+ proteins, the concatenated six AAA+ modules act as a single peptide, making it a unique feature in dynein. Other AAA+ proteins commonly have only one or two AAA+ units in a single polypeptide, so that the AAA+ ring is formed by the association of several AAA+ modules located on different polypeptides [63, 96]. The only known exception is midasin/Rea1, which is a dynein-related AAA+ protein that has six tandem AAA+ modules [18].
Modeling of Micro- and Nanoscale Electromechanical Systems and Devices
Published in Sergey Edward Lyshevski, Nano- and Micro-Electromechanical Systems, 2018
Complex three-dimensional organic complexes and assemblies in E. coli and S. typhimurium bacteria have been covered in previous sections. For example, the 45-nm E. coli nanorotor is the so-called MS ring, which consists of FliF and FliG proteins. These proteins’ geometry and folding are unknown. We assume that short-circuited nanowindings can be formed by these proteins. It should be emphasized that complex three-dimensional organic circuits (windings) can be engineered. As another example, consider the AAA (ATPases Associated with various cellular Activities) interacting protein superfamily. The AAA protein superfamily is characterized by a highly conserved module of more than 230 amino acid residues including an ATP binding consensus, present in one or two copies in the AAA proteins. The AAA proteins are found in all organisms and are essential for their functionality. Specific attention should be focused on the geometry and folding of different protein complexes and assemblies. Thus, the E. coli nanobiomotor and synthesized micro- and nanomachines can operate as induction nanomachines, as will be discussed later. (See Figure 6.39.)
Functional, conformational, topographical, and antioxidative properties of convectively- and freeze-dried sunflower protein and hydrolysate: a comparative investigation
Published in Drying Technology, 2023
Mokhtar Dabbour, Asmaa Hamoda, Hafida Wahia, Benjamin K. Mintah, Garba Betchem, Ronghai He, Haile Ma, Mohammad Fikry
The functions and antioxidant activities of protein/hydrolysate are mostly reliant on their AA composition. Table 2 shows the AA scores of SPm-s and SPHm-s isolates. All the dehydrated isolates were noticed to be rich in Glu and Asp ranging from 20.02 − 21.80% and 10.95 − 13.60%, respectively. Such findings agree very well with that recent report by Ghribi et al.[50] and Brishti et al.[19] who isolated chickpea protein and mung bean protein, respectively by freeze and convective drying. Moreover, Lys, reference to the remaining amino acids, is heat sensitive and convective drying relatively affect its content. CD preparations showed low amount of Lys content (compared with the respective FD samples) and this is possibly attributed to Maillard reaction,[51] which is induced by heated environment (40 and 50 °C) during convective dehydration process. The lowest L* and highest browning index values (observed in our earlier study[35]) validates the formation of Maillard product in CD isolates. Furthermore, the total antioxidative amino acid scores (TAAAc) and aromatic amino acid (AAAc) of the FD samples (FDSPm and FDSPHm) were higher than the respective CD powders; whilst the hydrophobic amino acid components (HAAc) of the FD samples were found to be lower. This may support why the lyophilized preparations displayed improved antioxidation effect and water binding efficacy, whereas reduced surface hydrophobicity and OBe (covered in this study), relative to the respective CD samples. This is in accordance with earlier reports that TAAAc and AAAc enhance the antioxidation function of proteins.[8,52] Additionally, TAAAc and AAAc of convectively- and freeze-dried SPHm were notably greater than the respective dried SPm-s, implying that enzymolysis could improve the antioxidative potential of SPm preparations by increasing their TAAAc and AAAc contents. This outcome in order agrees with the observation of DPPHRC, ABTSRE and RPW (Figure 6A–C).