3wky

Publication Abstract from PubMed

Phenoloxidase (PO), which is classified as a type 3 copper protein, catalyzes the hydroxylation of monophenol to o-diphenol and subsequent oxidation to the corresponding o-quinone. The geometry and coordination environment of the active site of the arthropod PO is very similar to that of the arthropod hemocyanin (Hc). However, unlike the POs, Hc is an oxygen carrier in crustaceans, and does not possess the PO activity in general. Recently, we identified a new type of proPO from a crustacean and designated it as proPObeta. This enzyme has many characteristics rather similar to Hc, such as its maturation, localization and oligomeric state. Here, we determined the crystal structure of proPObeta prepared from the hemolymph of kuruma prawns (Marsupenaeus japonicus) at 1.8 A resolution. M. japonicus proPObeta forms a homo-hexamer rather similar to arthropod Hc. The geometry of the active copper site in proPObeta was nearly identical to that of arthropod Hc. Furthermore, the well characterized 'place holder' phenylalanine was observed (Phe72). However, the accessibility to the active site differed in several ways. First, another phenylalanine residue which shields the active site by interacting with a copper-coordinated histidine in crustacean Hc was substituted by valine in proPObeta structure. Second, two tyrosine residues, Tyr208 and Tyr209, both of which are absent in Hc, show the alternative conformations and form a pathway accessible to the reaction center. Thus, the present crystal structure clarified the similarities and differences in the activity of two closely related proteins, PO and Hc. This article is protected by copyright. All rights reserved. STRUCTURED DIGITAL ABSTRACT: proPObeta and proPObeta bind by x-ray crystallography (View interaction).

Crystal structure of a crustacean prophenoloxidase provides a clue to understanding the functionality of the type 3 copper proteins.,Masuda T, Momoji K, Hirata T, Mikami B FEBS J. 2014 Apr 10. doi: 10.1111/febs.12812. PMID:24720693^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.