Formation of High-Order Structures in Solution by CBS-Pyrophosphatase from D. hafniense

To solve the question about the oligomeric state of wild-type CBS-pyrophosphatase (CBS-PPase) from D. hafniense, this enzyme has been studied using two independent structural methods: small-angle X-ray scattering (SAXS) and cryogenic transmission electron microscopy (cryoTEM). The formation of stable high-order structures (large helical associates) in a concentrated protein solution has been observed for the first time. It is also shown for the first time that the formation of these structures is a reversible process and the protein passes to the tetramer form (in which it usually exists in diluted solutions) at ligand attachment. The obtained results are important for understanding the functional features of CBS-PPase (in particular, gaining insight into the pathogenesis of some diseases).