Functional expression, monodispersity and conformational changes in the SBMV virus viral VPg on binding TFE.

Southern bean mosaic virus (SBMV) RNA purified from infected plants was used for cloning the viral genome-linked protein (VPg) and was subsequently expressed in Escherichia coli. Circular dichroism (CD), dynamic light scattering (DLS) and saturation transfer difference (STD) by nuclear magnetic resonance (NMR) measurements were employed to determine the degree of monodispersity and to investigate the conformational changes in the absence and presence of trifluoroethanol (TFE) which indicated increased helical content with increasing concentration of TFE. 8-Anilino-1-naphthalenesulfonic acid (ANS) was used as a probe to compare the unfolding regions of the protein before and after addition of TFE. The results indicated that although the TFE concentration influences VPg folding, it does not play a role in nucleotide binding and that the local solvent hydrophobicity causes significant conformational changes.

Crystal structure of Jararacussin-I: the highly negatively charged catalytic interface contributes to macromolecular selectivity in snake venom thrombin-like enzymes.

Snake venom serine proteinases (SVSPs) are hemostatically active toxins that perturb the maintenance and regulation of both the blood coagulation cascade and fibrinolytic feedback system at specific points, and hence, are widely used as tools in pharmacological and clinical diagnosis. The crystal structure of a thrombin-like enzyme (TLE) from Bothrops jararacussu venom (Jararacussin-I) was determined at 2.48 Å resolution. This is the first crystal structure of a TLE and allows structural comparisons with both the Agkistrodon contortrix contortrix Protein C Activator and the Trimeresurus stejnegeri plasminogen activator. Despite the highly conserved overall fold, significant differences in the amino acid compositions and three-dimensional conformations of the loops surrounding the active site significantly alter the molecular topography and charge distribution profile of the catalytic interface. In contrast to other SVSPs, the catalytic interface of Jararacussin-I is highly negatively charged, which contributes to its unique macromolecular selectivity.