1APX

CRYSTAL STRUCTURE OF RECOMBINANT ASCORBATE PEROXIDASE

Summary for 1APX

• Entry DOI: 10.2210/pdb1apx/pdb
• Descriptor: CYTOSOLIC ASCORBATE PEROXIDASE, POTASSIUM ION, PROTOPORPHYRIN IX CONTAINING FE, ... (4 entities in total)
• Functional Keywords: peroxidase
• Biological source: Pisum sativum (pea)
• Cellular location: Cytoplasm: P48534
• Total number of polymer chains: 4
• Total formula weight: 111012.58

Authors

Patterson, W.R.,Poulos, T.L. (deposition date: 1995-02-01, release date: 1996-03-08, Last modification date: 2024-02-07)

Primary citation

Patterson, W.R.,Poulos, T.L.
Crystal structure of recombinant pea cytosolic ascorbate peroxidase.
Biochemistry, 34:4331-4341, 1995

PubMed Abstract: 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.

PubMed: 7703247
DOI: 10.1021/bi00013a023

Experimental method

X-RAY DIFFRACTION (2.2 Å)