Integrative dynamic structural biology unveils conformers essential for the oligomerization of a large GTPase.

Guanylate binding proteins (GBPs) are soluble dynamin-like proteins. They undergo a conformational transition for GTP-controlled oligomerization and disrupt membranes of intra-cellular parasites to exert their function as part of the innate immune system of mammalian cells. We apply neutron spin echo, X-ray scattering, fluorescence, and EPR spectroscopy as techniques for integrative dynamic structural biology to study the structural basis and mechanism conformational transitions in the human GBP1 (hGBP1). We mapped hGBP1's essential dynamics from nanoseconds to milliseconds by motional spectra of sub-domains. We find a GTP-independent flexibility of the C-terminal effector domain in the μs-regime and resolve structures of two distinct conformers essential for an opening of hGBP1 like a pocketknife and oligomerization. Our results show that an intrinsic flexibility, a GTP-triggered association of the GTPase-domains, and the assembly-dependent GTP-hydrolysis are functional design principles that control hGBP1's reversible oligomerization.