2bq8 | pdb_00002bq8
CRYSTAL STRUCTURE OF HUMAN PURPLE ACID PHOSPHATASE WITH AN INHIBITORY CONFORMATION OF THE REPRESSION LOOP
Structural highlights
Disease[PPA5_HUMAN] Defects in ACP5 are the cause of spondyloenchondrodysplasia with immune dysregulation (SPENCDI) [MIM:607944]. A disease characterized by vertebral and metaphyseal dysplasia, spasticity with cerebral calcifications, and strong predisposition to autoimmune diseases. The skeletal dysplasia is characterized by radiolucent and irregular spondylar and metaphyseal lesions that represent islands of chondroid tissue within bone. Note=ACP5 inactivating mutations result in a functional excess of phosphorylated osteopontin causing deregulation of osteopontin signaling and consequential autoimmune disease.[1] [2] Function[PPA5_HUMAN] Involved in osteopontin/bone sialoprotein dephosphorylation. Its expression seems to increase in certain pathological states such as Gaucher and Hodgkin diseases, the hairy cell, the B-cell, and the T-cell leukemias. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedThe crystal structure of human purple acid phosphatase recombinantly expressed in Escherichia coli (rHPAP(Ec)) and Pichia pastoris (rHPAP(Pp)) has been determined in two different crystal forms, both at 2.2A resolution. In both cases, the enzyme crystallized in its oxidized (inactive) state, in which both Fe atoms in the dinuclear active site are Fe(III). The main difference between the two structures is the conformation of the enzyme "repression loop". Proteolytic cleavage of this loop in vivo or in vitro results in significant activation of the mammalian PAPs. In the crystals obtained from rHPAP(Ec), the carboxylate side-chain of Asp145 of this loop acts as a bidentate ligand that bridges the two metal atoms, in a manner analogous to a possible binding mode for a phosphate ester substrate in the enzyme-substrate complex. The carboxylate side-chain of Asp145 and the neighboring Phe146 side-chain thus block the active site, thereby inactivating the enzyme. In the crystal structure of rHPAP(Pp), the enzyme "repression loop" has an open conformation similar to that observed in other mammalian PAP structures. The present structures demonstrate that the repression loop exhibits significant conformational flexibility, and the observed alternate binding mode suggests a possible inhibitory role for this loop. Crystal structures of recombinant human purple Acid phosphatase with and without an inhibitory conformation of the repression loop.,Strater N, Jasper B, Scholte M, Krebs B, Duff AP, Langley DB, Han R, Averill BA, Freeman HC, Guss JM J Mol Biol. 2005 Aug 5;351(1):233-46. Epub 2005 Apr 26. PMID:15993892[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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