PDBsum entry 3hhs

Oxidoreductase

PDB id: 3hhs

Contents

Protein chains

669 a.a. *

656 a.a. *

Metals

_CU ×4

Waters ×1195

* Residue conservation analysis

PDB id:

3hhs

Name:

Oxidoreductase

Title:

Crystal structure of manduca sexta prophenoloxidase

Structure:

Phenoloxidase subunit 2. Chain: a. Synonym: propo-p2. Phenoloxidase subunit 1. Chain: b. Synonym: propo-p1. Ec: 1.14.18.1

Source:

Manduca sexta. Carolina sphinx,hornblower,tobacco hawkmoth,tomato hornworm. Organism_taxid: 7130. Other_details: tissue. Other_details: tissue

Resolution:

1.97Å R-factor: 0.156 R-free: 0.194

Authors:

Y.Li,Y.Wang,H.Jiang,J.Deng

Key ref:

Y.Li et al. (2009). Crystal structure of Manduca sexta prophenoloxidase provides insights into the mechanism of type 3 copper enzymes. Proc Natl Acad Sci U S A, 106, 17002-17006. PubMed id: 19805072 DOI: 10.1073/pnas.0906095106

Date:

17-May-09 Release date: 29-Sep-09

Protein chain

Q25519  (PRP2_MANSE) -  Phenoloxidase subunit 2 from Manduca sexta

Seq: 695 a.a.

Struc: 669 a.a.

Protein chain

O44249  (PRP1_MANSE) -  Phenoloxidase subunit 1 from Manduca sexta

Seq: 685 a.a.

Struc: 656 a.a.

Enzyme reactions

• Enzyme class: Chains A, B: E.C.1.14.18.1 - tyrosinase.
• Pathway: Melanin Biosynthesis
• Reaction:
  1. L-tyrosine + O2 = L-dopaquinone + H2O
  2. 2 L-dopa + O2 = 2 L-dopaquinone + 2 H2O
• Cofactor: Cu cation

Molecule diagrams generated from .mol files obtained from the KEGG ftp site

reference

DOI no: 10.1073/pnas.0906095106

Proc Natl Acad Sci U S A 106:17002-17006 (2009)

PubMed id: 19805072

Crystal structure of Manduca sexta prophenoloxidase provides insights into the mechanism of type 3 copper enzymes.

Y.Li, Y.Wang, H.Jiang, J.Deng.

ABSTRACT

Arthropod phenoloxidase (PO) generates quinones and other toxic compounds to sequester and kill pathogens during innate immune responses. It is also involved in wound healing and other physiological processes. Insect PO is activated from its inactive precursor, prophenoloxidase (PPO), by specific proteolysis via a serine protease cascade. Here, we report the crystal structure of PPO from a lepidopteran insect at a resolution of 1.97 A, which is the initial structure for a PPO from the type 3 copper protein family. Manduca sexta PPO is a heterodimer consisting of 2 homologous polypeptide chains, PPO1 and PPO2. The active site of each subunit contains a canonical type 3 di-nuclear copper center, with each copper ion coordinated with 3 structurally conserved histidines. The acidic residue Glu-395 located at the active site of PPO2 may serve as a general base for deprotonation of monophenolic substrates, which is key to the ortho-hydroxylase activity of PO. The structure provides unique insights into the mechanism by which type 3 copper proteins differ in their enzymatic activities, albeit sharing a common active center. A drastic change in electrostatic surface induced on cleavage at Arg-51 allows us to propose a model for localized PPO activation in insects.

Selected figure(s)

Figure 1.
Overall structure of M. sexta PPO. (A) The heterodimeric PPO is formed in a back-to-back mode. PPO1 and PPO2 are shown in green and yellow, respectively. (B) Domains of PPO2 are colored as follows: pro-region, purple; domain I, blue; domain II, yellow; domain III, green. The di-copper atoms are located in domain II and are shown as red spheres. The proteolytic site R51 residue is shown in the stick. The amino-terminus and carboxyl-terminus of PPO2 are indicated as N and C, respectively.

Figure 2.
Di-copper center in M. sexta PPO2. The active site of PPO2 can be superimposed well with that of oxygenated Limulus polyphemus hemocyanin (Lp-HC, PDB ID code 1OXY). The secondary structures of PPO2 are shown in the ribbon and colored in yellow. The 6 copper-coordinating His ligands are shown as sticks, with those from Lp-HC colored green. The di-copper atoms are shown as spheres: PPO2, red; Lp-HC, purple. The peroxide ion in Lp-HC is shown as brown spheres. Notice the unique E395 in PPO2, which is located near the substrate place holder F88. E395 could be a base for phenol deprotonation, which is key to the ortho-phenol hydroxylation activity of PPO.

Figures were selected by an automated process.