Solution structure and dynamics of the chimeric SH3 domains, SHH- and SHA-“Bergeracs”

Two chimeric proteins, SHН and SHA of the “SH3-Bergerac” family (where the β-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 β-hairpin in the region of the insertion was confirmed, the introduced extension of the polypeptide chain in SHН (∼ 17%) practically did not affect the total molecule topology. Interestingly, the introduced β-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 β-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.