Andreu Morales, José Manuel
91 837 3112 Extension: 4381/4380
Proteins from the tubulin superfamily of GTPases are essential to divide cells, to segregate DNA or for cytoskeletal functions. Tubulin-like proteins spread in eukaryotes, bacteria, plasmids and viruses; they include among other αβ-tubulin, γ-tubulin, bacterial tubulin BtubA/B, FtsZ and TubZ. They share a few sequence motifs and the same three-dimensional core structure, consisting of an N-terminal GTP binding domain and a GTPase activating domain connected by a central α-helix, but have divergent C-terminal secondary structures and flexible tails.
Each tubulin domain possibly evolved from two independent proteins, which would be equivalent to a current small GTPase (N-terminal domain) and its GTPase Activating Protein (GAP). Both fused into a single molecule that associated into a linear polymer based on the domain-domain interactions and had a polymerization-dependent GTPase activation mechanism. This common ancestral protein assembled into a polymer that performed mechanical work in a GTP-dependent manner, applying force to nucleic acid or to membrane in a primitive cell. This GTPase based molecular machine spread among different forms of life, where the different proteins and their assembly properties diverged (Figure 1).
Tubulin-like proteins, except γ-tubulin, typically associate head to tail into polar protofilaments with a 4 nm axial spacing between subunits that form different types of filaments (Figure 2). Their assembly and disassembly is directly linked to their function, forming characteristic subcellular structures such as spindles or division rings, and can produce motility without the assistance of motor proteins. Assembly involves the formation of a subunit-subunit interface where the GTP-binding domain of one subunit in a protofilament interacts with the GTPase activation domain of the next subunit, which complements the GTP pocket and induces GTP hydrolysis. Bound GDP and inorganic phosphate release trigger polymer disassembly, which is followed by subunit reloading with GTP. Polymer dynamics is based on assembly-disassembly events and shows different features depending on the precise mechanism involved, such as dynamic instability or treadmilling.
Our work focuses on understanding how these protein assembly machines work, and targeting them with new anticancer (Figure 3) and antibacterial molecules; we use biochemical, crystallography, NMR, computational, microbiological, fluorescence, electron microscopy and synthetic approaches at the CIB and collaborating labs.