Crystal structures of PI3K-C2alpha PX domain indicate conformational change associated with ligand binding.

ABSTRACT: BACKGROUND:PX domains have specialized protein structures involved in binding of phosphoinositides (PIs). Through binding to the various PIs PX domains provide site-specific membrane signals to modulate the intracellular localisation and biological activity of effector proteins. Several crystal structures of these domains are now available from a variety of proteins. All PX domains contain a canonical core structure with main differences exhibited within the loop regions forming the phosphoinositide binding pockets. It is within these areas that the molecular basis for ligand specificity originates. RESULTS:We now report two new structures of PI3K-C2alpha PX domain that crystallised in a P3121 space group. The two structures, refined to 2.1 A and 2.5 A, exhibit significantly different conformations of the phosphoinositide-binding loops. Unexpectedly, in one of the structures, we have detected a putative-ligand trapped in the binding site during the process of protein purification and crystallisation. CONCLUSION:The two structures reported here provide a more complete description of the phosphoinositide binding region compared to the previously reported 2.6 A crystal structure of human PI3K-C2alpha PX where this region was highly disordered. The structures enabled us to further analyse PI specificity and to postulate that the observed conformational change could be related to ligand-binding.

SUBMITTER: Parkinson GN 

PROVIDER: S-EPMC2292188 | biostudies-literature | 2008 Feb

REPOSITORIES: biostudies-literature