RESUMEN
Two chimeric proteins, SHcapital EN, Cyrillic and SHA of the "SH3-Bergerac" family (where the beta-turn N47D48 in spectrin SH3 domain was substituted for KITVNGKTYE or KATANGKTYE sequences, respectively), were analyzed by high-resolution NMR to resolve their spatial structures and to analyze their dynamics. Although the presence of a stable beta-hairpin in the region of the insertion was confirmed, the introduced extension of the polypeptide chain in SHcapital EN, Cyrillic (approximately 17%) practically did not affect the total molecule topology. Interestingly, the introduced beta-hairpin had higher mobility in comparison with other protein regions. Finally, we performed a disorder prediction with the PONDR VSL2 algorithm and discovered that the inserted beta-hairpin in both SHH and SHA proteins exhibited significant propensity for intrinsic disorder and therefore for high mobility. In agreement with the experimental data, the predisposition for the increased intramolecular mobility was noticeably higher in SHA.
Asunto(s)
Dominios Homologos src , Secuencia de Aminoácidos , Modelos Moleculares , Datos de Secuencia Molecular , Resonancia Magnética Nuclear Biomolecular , Pliegue de Proteína , Estructura Secundaria de Proteína , Proteínas Recombinantes de Fusión/química , Proteínas Recombinantes de Fusión/genética , Soluciones , Termodinámica , Dominios Homologos src/genéticaRESUMEN
Aggregation and subsequent development of protein deposition diseases originate from conformational changes in corresponding amyloidogenic proteins. Many proteins unrelated to amyloidoses also fibrillate at the appropriate conditions. These proteins serve as a model for studying the processes of protein misfolding, oligomerization and fibril formation. The accumulated data support the model where protein fibrillogenesis proceeds via the formation of a relatively unfolded amyloidogenic conformation. The urea-induced unfolding of bovine carbonic anhydrase II, BCA II, is characterized by a combination of high-resolution NMR, circular dichroism spectroscopy and small angle X-ray scattering. It is shown that the formation of associates of protein molecules in complex with solvent (water and urea), APS, takes place in the presence of 4-6 M urea. The subsequent increase in urea concentration to 8 M is accompanied by a disruption of APS and leads to a complete unfolding of a protein molecule. Analysis of BCA II self-association in the presence of 4.2 M urea revealed that APS are relatively large mostly beta-structural blocks with the averaged molecular mass of 190-220 kDa. This work also demonstrates some novel NMR-based methodological approaches that provide useful information on protein self-association.
