1wda: Difference between revisions

[[Image:1wda.gif|left|200px]]<br /><applet load="1wda" size="350" color="white" frame="true" align="right" spinBox="true"  

Peptidylarginine deiminase 4 (PAD4) is a Ca(2+)-dependent enzyme that catalyzes the conversion of protein arginine residues to citrulline. Its gene is a susceptibility locus for rheumatoid arthritis. Here we present the crystal structure of Ca(2+)-free wild-type PAD4, which shows that the polypeptide chain adopts an elongated fold in which the N-terminal domain forms two immunoglobulin-like subdomains, and the C-terminal domain forms an alpha/beta propeller structure. Five Ca(2+)-binding sites, none of which adopt an EF-hand motif, were identified in the structure of a Ca(2+)-bound inactive mutant with and without bound substrate. These structural data indicate that Ca(2+) binding induces conformational changes that generate the active site cleft. Our findings identify a novel mechanism for enzyme activation by Ca(2+) ions, and are important for understanding the mechanism of protein citrullination and for developing PAD-inhibiting drugs for the treatment of rheumatoid arthritis.

1WDA is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Homo_sapiens Homo sapiens] with <scene name='pdbligand=CA:'>CA</scene>, <scene name='pdbligand=SO4:'>SO4</scene> and <scene name='pdbligand=BAG:'>BAG</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Protein-arginine_deiminase Protein-arginine deiminase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.5.3.15 3.5.3.15] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1WDA OCA].  

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