4b6w

Publication Abstract from PubMed

Tubulin-binding cofactor B (TBC-B) is implicated in the presentation of alpha-tubulin ready to polymerize, and at the correct levels to form microtubules. Bioinformatics analyses including secondary structure prediction, circular dichroism (CD) and crystallography are combined to characterize the molecular architecture of Trypanosoma brucei TBC-B. An efficient recombinant expression system was prepared, material purified and characterized by CD. Extensive crystallization screening, allied with the use of limited proteolysis, led to structures of the N-terminal ubiquitin-like (Ubl) and C-terminal CAP-Gly (cytoskeleton associated protein with glycine-rich segment) domains at 2.35 and 1.6 A resolution respectively. These are compact globular domains that appear to be linked by a flexible segment. The Ubl domain contains two lysines that are spatially conserved with residues known to participate in ubiquitinylation so may represent a module, that through covalent attachment regulates the signaling and/or protein degradation associated with the control of microtubule assembly, catastrophe or function. The TBC-B CAP-Gly segment, a known tubulin-binding structure, is the only such domain encoded by the T. brucei genome. Interestingly, in the crystal structure the peptide-binding groove of this domain forms intermolecular contacts with the C-terminus of a symmetry-related molecule; an association that may mimic interactions with the C-terminus of alpha-tubulin or other physiologically relevant partners. The interaction of TBC-B with the alpha-tubulin C-terminus may in particular protect from post-translational modifications, or simply assist in the shepherding of the protein into polymerization. This article is protected by copyright. All rights reserved.

The architecture of Trypanosoma brucei tubulin-binding cofactor B and implications for function.,Fleming JR, Morgan RE, Fyfe PK, Kelly SM, Hunter WN FEBS J. 2013 Apr 30. doi: 10.1111/febs.12308. PMID:23627368^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.