Solution structure of a ubiquitin-like domain from tubulin-binding cofactor B.

Proper folding and assembly of tubulin alphabeta-heterodimers involves a stepwise progression mediated by a group of protein cofactors A through E. Upon release of the tubulin monomers from the chaperonin CCT, they are acted upon by each cofactor in the folding pathway through a unique combination of protein interaction domains. Three-dimensional structures have previously been reported for cofactor A and the C-terminal CAP-Gly domain of cofactor B (CoB). Here we report the NMR structure of the N-terminal domain of Caenorhabditis elegans CoB and show that it closely resembles ubiquitin as was recently postulated on the basis of bioinformatic analysis (Grynberg, M., Jaroszewski, L., and Godzik, A. (2003) BMC Bioinformatics 4, 46). CoB binds partially folded alpha-tubulin monomers, and a putative tubulin-binding motif within the N-terminal domain is identified from sequence and structure comparisons. Based on modeling of the homologous cofactor E ubiquitin-like domain, we hypothesize that cofactors B and E may associate via their beta-grasp domains in a manner analogous to the PB1 and caspase-activated deoxyribonuclease superfamily of protein interaction domains.

Structural genomics for Caenorhabditis elegans: high throughput protein expression analysis.

The structural genomics initiatives have begun with the aim to create a so-called "basic set library" of protein folds that will be used to improve protein prediction methods. Such a library is thought to require the determination of up to 10,000 new structures, including representative structures of several sequence variants from each protein fold. To meet this goal in a reasonable time frame and cost, automated systems must be utilized to clone and to identify the soluble recombinant proteins contained in multiple genomes. This paper presents such a system, developed using the genome of Caenorhabditis elegans (19,099 genes) as a model eukaryotic organism for structural genomics. This system successfully automates nearly all aspects of recombinant protein expression analysis including subcloning, bacterial growth, recombinant protein expression, protein purification, and scoring protein solubility.

Crystal structure of the cytoskeleton-associated protein glycine-rich (CAP-Gly) domain.

Cytoskeleton-associated proteins (CAPs) are involved in the organization of microtubules and transportation of vesicles and organelles along the cytoskeletal network. A conserved motif, CAP-Gly, has been identified in a number of CAPs, including CLIP-170 and dynactins. The crystal structure of the CAP-Gly domain of Caenorhabditis elegans F53F4.3 protein, solved by single wavelength sulfur-anomalous phasing, revealed a novel protein fold containing three beta-sheets. The most conserved sequence, GKNDG, is located in two consecutive sharp turns on the surface, forming the entrance to a groove. Residues in the groove are highly conserved as measured from the information content of the aligned sequences. The C-terminal tail of another molecule in the crystal is bound in this groove.