1djh
From Proteopedia
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PHOSPHOINOSITIDE-SPECIFIC PHOSPHOLIPASE C-DELTA1 FROM RAT COMPLEXED WITH BARIUM
Overview
We have determined the crystal structures of complexes of, phosphoinositide-specific phospholipase C-delta1 from rat with calcium, barium, and lanthanum at 2.5-2.6 A resolution. Binding of these metal ions, is observed in the active site of the catalytic TIM barrel and in the, calcium binding region (CBR) of the C2 domain. The C2 domain of PLC-delta1, is a circularly permuted topological variant (P-variant) of the, synaptotagmin I C2A domain (S-variant). On the basis of sequence analysis, we propose that both the S-variant and P-variant topologies are present, among other C2 domains. Multiple adjacent binding sites in the C2 domain, were observed for calcium and the other metal/enzyme complexes. The, maximum number of binding sites observed was for the calcium analogue, lanthanum. This complex shows an array-like binding of three lanthanum, ions (sites I-III) in a crevice on one end of the C2 beta-sandwich., Residues involved in metal binding are contained in three loops, CBR1, CBR2, and CBR3. Sites I and II are maintained in the calcium and barium, complexes, whereas sites II and III coincide with a binary calcium binding, site in the C2A domain of synaptotagmin I. Several conformers for CBR1 are, observed. The conformation of CBR1 does not appear to be strictly, dependent on metal binding; however, metal binding may stabilize certain, conformers. No significant structural changes are observed for CBR2 or, CBR3. The surface of this ternary binding site provides a cluster of, freely accessible liganding positions for putative phospholipid ligands of, the C2 domain. It may be that the ternary metal binding site is also a, feature of calcium-dependent phospholipid binding in solution. A ternary, metal binding site might be a conserved feature among C2 domains that, contain the critical calcium ligands in their CBR's. The high, cooperativity of calcium-mediated lipid binding by C2 domains described, previously is explained by this novel type of calcium binding site.
About this Structure
1DJH is a Single protein structure of sequence from Rattus norvegicus with BA and ACT as ligands. Active as Phosphoinositide phospholipase C, with EC number 3.1.4.11 Full crystallographic information is available from OCA.
Reference
A ternary metal binding site in the C2 domain of phosphoinositide-specific phospholipase C-delta1., Essen LO, Perisic O, Lynch DE, Katan M, Williams RL, Biochemistry. 1997 Mar 11;36(10):2753-62. PMID:9062102
Page seeded by OCA on Tue Nov 20 13:19:57 2007
