PDBsum entry 1euo

Signaling protein

PDB id: 1euo

Contents

Protein chain

180 a.a. *

Ligands

HEM-NH3

Waters ×80

* Residue conservation analysis

PDB id:

1euo

Name:

Signaling protein

Title:

Crystal structure of nitrophorin 2 (prolixin-s)

Structure:

Nitrophorin 2. Chain: a. Synonym: prolixin-s. Engineered: yes

Source:

Rhodnius prolixus. Organism_taxid: 13249. Organ: salivary gland. Gene: salivary gland cdna. Expressed in: escherichia coli. Expression_system_taxid: 562.

Resolution:

2.00Å R-factor: 0.195 R-free: 0.246

Authors:

J.F.Andersen,W.R.Montfort

Key ref:

J.F.Andersen and W.R.Montfort (2000). The crystal structure of nitrophorin 2. A trifunctional antihemostatic protein from the saliva of Rhodnius prolixus. J Biol Chem, 275, 30496-30503. PubMed id: 10884386 DOI: 10.1074/jbc.M002857200

Date:

17-Apr-00 Release date: 10-May-00

Protein chain

Q26241  (NP2_RHOPR) -  Nitrophorin-2 from Rhodnius prolixus

Seq: 202 a.a.

Struc: 180 a.a.*

* PDB and UniProt seqs differ at 1 residue position (black cross)

DOI no: 10.1074/jbc.M002857200

J Biol Chem 275:30496-30503 (2000)

PubMed id: 10884386

The crystal structure of nitrophorin 2. A trifunctional antihemostatic protein from the saliva of Rhodnius prolixus.

J.F.Andersen, W.R.Montfort.

ABSTRACT

Nitrophorin 2 (NP2) (also known as prolixin-S) is a salivary protein that transports nitric oxide, binds histamine, and acts as an anticoagulant during blood feeding by the insect Rhodnius prolixus. The 2.0-A crystal structure of NP2 reveals an eight-stranded antiparallel beta-barrel containing a ferric heme coordinated through His(57), similar to the structures of NP1 and NP4. All four Rhodnius nitrophorins transport NO and sequester histamine through heme binding, but only NP2 acts as an anticoagulant. Here, we demonstrate that recombinant NP2, but not recombinant NP1 or NP4, is a potent anticoagulant; recombinant NP3 also displays minor activity. Comparison of the nitrophorin structures suggests that a surface region near the C terminus and the loops between beta strands B-C and E-F is responsible for the anticoagulant activity. NP2 also displays larger NO association rates and smaller dissociation rates than NP1 and NP4, which may result from a more open and more hydrophobic distal pocket, allowing more rapid solvent reorganization on ligand binding. The NP2 protein core differs from NP1 and NP4 in that buried Glu(53), which allows for larger NO release rates when deprotonated, hydrogen bonds to invariant Tyr(81). Surprisingly, this tyrosine lies on the protein surface in NP1 and NP4.

Selected figure(s)

Figure 3.
Fig. 3. Ribbon diagram of the NP2 structure. The eight strands of the -barrel are labeled A-H, and the heme, bound in the central cavity of the protein, is shown in black.

Figure 4.
Fig. 4. Detail of the heme-binding region of NP2. The view is from the back of the heme pocket. Hydrophobic residues lining the distal pocket are shown along with the distal ligand (either ammonia or water). On the proximal side of the heme, the ligand His^57 is shown along with the hydrogen bonding network involving Asn^67 and an intervening water molecule. Residues hydrogen bonding with the heme propionate groups are also shown. Oxygens are indicated by stippled spheres, and nitrogens are indicated by larger open spheres.

The above figures are reprinted by permission from the ASBMB: J Biol Chem (2000, 275, 30496-30503) copyright 2000.

Figures were selected by the author.