Crystal structure of a Schistosoma mansoni septin reveals the phenomenon of strand slippage in septins dependent on the nature of the bound nucleotide [Protein Structure and Folding]

January 24th, 2014 by Zeraik, A. E., Pereira, H. M., Santos, Y. V., Brandao–Neto, J., Spoerner, M., Santos, M. S., Colnago, L. A., Garratt, R. C.., Arau&jnodot;o, A. P. U., DeMarco, R.

Septins are filament forming GTP-binding proteins involved in important cellular events such as cytokinesis, barrier formation and membrane remodeling. Here, we present two crystal structures of the GTPase domain of a Schistosoma mansoni septin (SmSEPT10); one bound to GDP and the other to GTP. The structures have been solved at an unprecedented resolution for septins (1.93 and 2.1 Å respectively) which has allowed for unambiguous structural assignment of regions previously poorly defined. Consequently we provide a reliable model for functional interpretation and a solid foundation for future structural studies. On comparing the two complexes, we observe for the first time the phenomenon of a strand slippage in septins. Such slippage generates a front-back communication mechanism between the G and NC interfaces. This data provides a novel mechanistic framework for the influence of nucleotide binding to the GTPase domain, opening new possibilities for the study of the dynamics of septin filaments.
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