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Homeostasis of Dopamine
Published in Nira Ben-Jonathan, Dopamine, 2020
The DAT gene encodes an 80-kDa glycoprotein, made of 620 amino acids, with no known isoforms. The proposed membrane topology of DAT was based on hydrophobic sequence analysis, sequence similarities with the leucine transporter, X-ray crystallography of the Drosophila melanogaster DAT (albeit it has only 50% homology with hDAT), and in silico modeling. Collectively, these approaches predicted that the DAT is configured in 12 transmembrane domains (TMDs), with a large extracellular loop between the third and fourth TMDs, and cytoplasmic N- and C-termini (Figure 1.8).
Torovirus
Published in Dongyou Liu, Handbook of Foodborne Diseases, 2018
Ziton Abdulrida Ighewish Al-Khafaji, Ghanim Aboud Al-Mola
The M protein gene is 699 nt long and encodes a 26.5 kDa protein that in its N-terminal part contains the three membrane-spanning α-helices which are so characteristic for coronavirus M proteins [24]. The 4.5 kDa difference between the calculated and observed sizes of the M protein is accounted for by aberrant migration in polyacrylamide gels, due probably to the extreme hydrophobicity of the protein. The membrane topology of the M protein has been inferred from in vitro translation studies using the M protein itself and a hybrid protein, which contains a C-terminal tag, located at the cytoplasmic face of the endoplasmic reticulum [24]. After in vitro translation in the presence of microsomes, about 85% of each protein was resistant to protease K digestion. Since the BEV M protein does not contain an N-terminal signal sequence, one of the hydrophobic transmembrane domains is assumed to function as an internal signal sequence. Like coronavirus M proteins, the BEV M hybrid carrying the C-terminal tag accumulated in intracellular membranes during transient expression experiments. Thus, the torovirus M protein may play a role in the intracellular budding process, as suggested for its coronavirus counterpart [25–27].
Organ Cross-Talk Regulates (Brain) Insulin Action
Published in André Kleinridders, Physiological Consequences of Brain Insulin Action, 2023
Adiponectin regulates glucose and lipid homeostasis, targeting the skeletal muscle, liver, and adipose tissue by acting on adiponectin receptors (AdipoRs). Both AdipoR1 and AdipoR2 are ubiquitously expressed and serve as a receptor for globular and full-length adiponectin existing as at least three species of multimers (31). Unlike the classical G-protein-coupled receptors (GPCRs), the AdipoRs have an inverted membrane topology with an internal (cytoplasmatic) NH2-terminus and an external (extracellular) COOH-terminus (40). In addition, another receptor named T-cadherin is also known to sense hexameric and HMW adiponectin complexes, but not trimeric or globular adiponectin (41). Whereas AdipoR1 has a high affinity for globular adiponectin and is most abundantly expressed in the skeletal muscle, where it activates AMPK and promotes fatty acid oxidation as well as glucose uptake; AdipoR2 is predominantly expressed in the liver and primarily senses full-length adiponectin, leading to AMPK-dependent and -independent suppression of glucose production through a decrease in the expression of gluconeogenic enzymes (e.g. phosphoenolpyruvate carboxylase and glucose-6-phosphatase) (40, 42). In monocyte-derived macrophages from human adipose tissue, adiponectin increases the secretion of the anti-inflammatory cytokine interleukin-10 (43). Consistent with this finding, an adipose tissue-specific overexpression of adiponectin in leptin-deficient (ob/ob) mice reduced systemic inflammation and greatly increased subcutaneous fat mass containing smaller adipocytes, leading to increased insulin sensitivity and improved pancreatic β-cell survival (44). It is therefore hypothesized that the ectopic fat accumulation in the liver and the associated insulin resistance is caused by an inability to expand subcutaneous adipose tissue appropriately, with adiponectin as the underlying signal to promote the storage of triglycerides preferentially in the adipose tissue (44).
Efflux proteins at the blood–brain barrier: review and bioinformatics analysis
Published in Xenobiotica, 2018
Massoud Saidijam, Fatemeh Karimi Dermani, Sareh Sohrabi, Simon G. Patching
The amino acid composition of a protein and of its distinct domains is important for defining folding, structure, interactions with environment and with substrates and ligands, molecular mechanism and function. Hence, an analysis of amino acid composition can be used in the identification and classification of different types of proteins. For example, in distinguishing membrane proteins from non-membrane proteins, the former of which contain higher contents of hydrophobic residues to satisfy favourable thermodynamic interactions with the lipid bilayer. Amino acid composition has been used to assist classification and/or define substrate specificities of GPCRs (Gao et al., 2013; Zia-Ur-Rehman & Khan, 2012; Zia-Ur-Rehman et al., 2013), ion channels (Lin & Ding, 2011; Schaadt & Helms, 2012) and transporters (Liou et al., 2015; Mishra et al., 2014; Saidijam & Patching, 2015; Saidijam et al., 2017a). Futhermore, most of the membrane topology prediction methods use an element of amino acid composition for identifying transmembrane domains.
Proteomic analysis of the cardiac extracellular matrix: clinical research applications
Published in Expert Review of Proteomics, 2018
Merry L. Lindsey, Mira Jung, Michael E. Hall, Kristine Y. DeLeon-Pennell
In addition to traditional methods for evaluation of membrane topology, proteomics can be used to provide information about membrane topography [31]. This includes location of N-glycosylation and proteolytic sites, which are relevant to ECM studies [2]. Assessment for N-glycosylation sites can be used for evaluation of membrane topology [69,70]. Gundry et al. used this method to determine the orientation of transmembrane glycoprotein ZIP14, which was incorrectly assigned in SwissProt and has since been corrected [69]. The Gundry lab also uses this approach to identify novel markers of stem cells [71,72]. Our lab used a similar approach to provide new topologic information on hundreds of membrane and ECM proteins, including identifying four novel N-glycosites for β1 Integrin (N212, N406, N481, and N520) in post-MI infarct tissue [31]. In order to identify new protein partners, global approaches for large-scale proteomic profiling should be followed up with other methodologies such as nuclear magnetic resonance. To map protein–protein interactions using MS technology, the intact protein complex must first be affinity purified before digestion and MS analysis [2,73].
Genetic engineering strategies for construction of multivalent chimeric VLPs vaccines
Published in Expert Review of Vaccines, 2020
Xinnuo Lei, Xiong Cai, Yi Yang
Transmembrane domain and cytoplasmic tail (TM/CT) grafting is the most commonly used strategy for incorporation of foreign proteins or protein domains into the defined viral envelope proteins to generate chi-eVLPs. As mentioned above, most envelope proteins of virus, belonging to transmembrane proteins that are stably anchored in the viral envelope, generally are composed of three domains (ectodomain, TM, and CT). Based on membrane topology, transmembrane proteins can be further classified into two groups, single-pass and multi-pass membrane proteins (Figure 2) [59].