China
Africa
Explore chapters and articles related to this topic
The Binding of Diethylstilbestrol to Transthyretin – A Crystallographic Model
Published in Gilles Grateau, Robert A. Kyle, Martha Skinner, Amyloid and Amyloidosis, 2004
E. Morais-de-Sá, P.J.B. Pereira, M.J. Saraiva, A.M. Damas
Dissociation of the TTR tetramer is probably essential in the mechanism of amyloid formation and since the binding of small molecules to the TTR central channel stabilizes the tetramer, several compounds are being studied as a prospect for a non invasive therapeutic approach (1,2). Diethylstilbestrol (DES) is a synthetic estrogen that was shown to be a competitive inhibitor for thyroid hormone binding to TTR and therefore it may have a stabilizing effect over the protein quaternary structure (3). The crystallographic structure of TTR, first determined by C.Blake and collaborators, revealed a tetramer formed by four identical subunits, each of them consisting of two four stranded β-sheets (4).
Profile of respiratory syncytial virus prefusogenic fusion protein nanoparticle vaccine
Published in Expert Review of Vaccines, 2021
Brittani N. Blunck, Wanderson Rezende, Pedro A. Piedra
The innovation of this construct extends beyond its nanoparticle arrangement. The structure of each F protein trimer resembles aspects of both the pre-fusion and post-fusion native conformations. The protein quaternary structure is recognized by monoclonal antibodies targeting antigenic sites unique to the pre-fusion conformation (sites Ø and VIII), to antigenic sites shared between pre- and post-fusion (sites II and IV), and also to p27 (present in partially cleaved F proteins), and was recently found to elicit antibody response during RSV infections [62]. This unique conformation of the F protein was therefore termed ‘prefusogenic’ to reflect this altered antibody binding profile that stimulates more broadly neutralizing antibody to that of either the ‘pre-fusion’ or ‘post-fusion’ conformations [61,63].
Completion of the gut microbial epi-bile acid pathway
Published in Gut Microbes, 2021
Heidi L. Doden, Patricia G. Wolf, H. Rex Gaskins, Karthik Anantharaman, João M. P. Alves, Jason M. Ridlon
Edenharder & Pfützner (1988) initially characterized NADP(H)-dependent 12β-HSDH from crude extracts of the fecal isolate C. paraputrificum strain D 762–06, with differing results from our findings.19 Gel filtration analysis of crude extract from C. paraputrificum strain D 762–06 suggested a molecular mass of 126 kDa, whereas our current work with Cp12β-HSDH from ATCC 25780 is estimated at 54.6 KDa by gel filtration chromatography. The strain used in this study, C. paraputrificum ATCC 25780, was also isolated from feces.51 It is possible that these are the same NADP(H)-dependent enzymes by sequence from two different strains of C. paraputrificum and that the recombinant protein quaternary structure is unstable, resulting in a dimeric form in our study. Alternatively, these bacterial strains may have distinct versions of 12β-HSDH with different amino acid sequences, as we have shown previously for 12α-HSDH from Eggerthella lenta.35,52 Indeed, the 12β-HSDH from C. paraputrificum strain D 762–06 was reported to be partially membrane associated, whereas hydropathy prediction by TMHMM v. 2.0 found no evidence of transmembrane domains in Cp12β-HSDH. In addition, pH optima for the conversion of 12-oxoLCA between Cp12β-HSDH (7.0) and the native 12β-HSDH (10.0) from strain D 762–06 differed. Oxidation of epiDCA was optimal at pH 7.5 for Cp12β-HSDH, and reported as pH 7.8 for the crude native enzyme from strain D 762–06.19 Further work will be needed to determine if distinct bile acid 12β-HSDHs are present in C. paraputrificum strains.
High-yield synthesis and purification of recombinant human GABA transaminase for high-throughput screening assays
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2021
Mingu Gordon Park, Ah-reum Han, Su Yeon Kim, Tai Young Kim, Ho Min Kim, C. Justin Lee
The mechanisms of irreversible inhibition of gabaculine and vigabatrin are well-known. The irreversible inhibition is observed when gabaculine is covalently linked to PLP and this adduct is bound tightly to the active site of GABA-T47. Similarly, vigabatrin forms a covalent ternary adduct with the active site Lys-329 and PLP cofactor to irreversibly inhibit GABA-T41. However, the values of half-maximal inhibitory concentration (IC50) of gabaculine and vigabatrin have not been determined with human GABA-T, due to the lack of availability. To test whether IC50 values of gabaculine and vigabatrin for GABA-T differ by the species and protein quaternary structure, we recorded kinetic profiles of human and bacterial GABA-T reactions with gabaculine or vigabatrin at different concentrations in the absence or presence of 2-ME (Figures 4(A) and 5(A)). Dose-response curves were plotted by using the data from the linear initial phase of the reactions. IC50 values of gabaculine for human GABA-T and bacterial GABA-T in the absence of 2-ME (multimeric form) were 0.22 and 0.19 µM, respectively (Figure 4(B)). IC50 values of gabaculine for human GABA-T and bacterial GABA-T in the presence of 2-ME (monomeric form) were similar as well; 0.12 and 0.13 µM, respectively (Figure 4(C)). On the other hand, in the absence of 2-ME, IC50 of vigabatrin for bacterial GABA-T (631.3 µM) was higher than for human GABA-T (8.93 µM) (Figure 5(B)), indicating that the human GABA-T is more sensitive to vigabatrin than the bacterial GABA-T. Likewise, in the presence of 2-ME, IC50 of vigabatrin for bacterial GABA-T (14,202 µM) was higher than for human GABA-T (70.3 µM) (Figure 5(C)). These results indicate that although the human and bacterial GABA-T showed similar sensitivity to gabaculine, the human GABA-T in homodimeric form showed 70-fold higher sensitivity to vigabatrin than the bacterial GABA-T in multimeric form. In addition, the difference in sensitivity to vigabatrin between the human and bacterial GABA-T significantly increased from 70-fold in the multimeric form to 202-fold in the monomeric form. Taken together, the human and bacterial GABA-T have profoundly different characteristics, such that the human GABA-T cannot be substituted with the bacterial GABA-T, especially when searching for GABA-T modulators for human use.