1cck: Difference between revisions

The crystal structure of recombinant pea cytosolic ascorbate peroxidase, has been refined to an R = 0.19 for data between 8.0 and 2.2 A resolution, and magnitude of F > or = 2 sigma(magnitude of F). The refined model, consists of four ascorbate peroxidase monomers consisting of 249 residues, per monomer assembled into two homodimers, with one heme group per, monomer. The ascorbate peroxidase model confirms that the pea cytosolic, enzyme is a noncovalent homodimer held together by a series of ionic, interactions arranged around the 2-fold noncrystallographic dimer axis. As, expected from the high level of sequence identity (33%), the overall fold, of the ascorbate peroxidase monomer closely resembles that of cytochrome c, peroxidase. The average root mean square differences for 137 helical, alpha-carbon atoms between the four ascorbate peroxidase monomers and, cytochrome c peroxidase and for 249 topologically equivalent alpha-carbon, atoms are 0.9 and 1.3 A, respectively. The active site structures are also, the same, including the hydrogen-bonding interactions between the proximal, His ligand, a buried Asp residue, and a Trp residue, whose indole ring is, parallel to and in contact with the proximal His ligand just under the, heme ring. This proximal Trp residue is thought to be the site of free, radical formation in cytochrome c peroxidase compound I and is also, essential for enzyme activity. The corresponding Trp in ascorbate, peroxidase, Trp179, occupies exactly the same position. The most, interesting, and possibly functionally important, difference between the, two peroxidases is the presence of a cation binding site in ascorbate, peroxidase located approximately 8 A from the alpha-carbon atom of Trp179.

1CCK is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Saccharomyces_cerevisiae Saccharomyces cerevisiae] with HEM as [http://en.wikipedia.org/wiki/ligand ligand]. Active as [http://en.wikipedia.org/wiki/Cytochrome-c_peroxidase Cytochrome-c peroxidase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=1.11.1.5 1.11.1.5] Structure known Active Site: AVE. Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=1CCK OCA].  

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