PDBsum entry 3m86

Protein binding

PDB id: 3m86

Contents

Protein chains

111 a.a. *

104 a.a. *

Ligands

1PE

SO4 ×2

Metals

_CL ×2

Waters ×187

* Residue conservation analysis

PDB id:

3m86

Name:

Protein binding

Title:

Crystal structure of the cysteine protease inhibitor, ehicp2, from entamoeba histolytica

Structure:

Amoebiasin-2. Chain: a, b. Synonym: cysteine protease inhibitor 2, ehicp2, icp-2. Engineered: yes

Source:

Entamoeba histolytica. Organism_taxid: 294381. Strain: hm-1:imss. Gene: ehi_040460, icp2. Expressed in: escherichia coli. Expression_system_taxid: 562.

Resolution:

1.65Å R-factor: 0.185 R-free: 0.214

Authors:

S.Lara-Gonzalez,L.E.Casados-Vazquez,L.G.Brieba

Key ref:

L.E.Casados-Vázquez et al. (2011). Crystal structure of the cysteine protease inhibitor 2 from Entamoeba histolytica: functional convergence of a common protein fold. Gene, 471, 45-52. PubMed id: 20951777

Date:

17-Mar-10 Release date: 02-Feb-11

Protein chain

C4M2H5  (C4M2H5_ENTHI) -  Amoebiasin-2 from Entamoeba histolytica (strain ATCC 30459 / HM-1:IMSS / ABRM)

Seq: 123 a.a.

Struc: 111 a.a.*

Protein chain

C4M2H5  (C4M2H5_ENTHI) -  Amoebiasin-2 from Entamoeba histolytica (strain ATCC 30459 / HM-1:IMSS / ABRM)

Seq: 123 a.a.

Struc: 104 a.a.*

* PDB and UniProt seqs differ at 8 residue positions (black crosses)

Gene 471:45-52 (2011)

PubMed id: 20951777

Crystal structure of the cysteine protease inhibitor 2 from Entamoeba histolytica: functional convergence of a common protein fold.

L.E.Casados-Vázquez, S.Lara-González, L.G.Brieba.

ABSTRACT

Cysteine proteases (CP) are key pathogenesis and virulence determinants of protozoan parasites. Entamoeba histolytica contains at least 50 cysteine proteases; however, only three (EhCP1, EhCP2 and EhCP5) are responsible for approximately 90% of the cysteine protease activity in this parasite. CPs are expressed as inactive zymogens. Because the processed proteases are potentially cytotoxic, protozoan parasites have developed mechanisms to regulate their activity. Inhibitors of cysteine proteases (ICP) of the chagasin-like inhibitor family (MEROPS family I42) were recently identified in bacteria and protozoan parasites. E. histolytica contains two ICP-encoding genes of the chagasin-like inhibitor family. EhICP1 localizes to the cytosol, whereas EhICP2 is targeted to phagosomes. Herein, we report two crystal structures of EhICP2. The overall structure of EhICP2 consists of eight β-strands and closely resembles the immunoglobulin fold. A comparison between the two crystal forms of EhICP2 indicates that the conserved BC, DE and FG loops form a flexible wedge that may block the active site of CPs. The positively charged surface of the wedge-forming loops in EhICP2 contrasts with the neutral surface of the wedge-forming loops in chagasin. We postulate that the flexibility and positive charge observed in the DE and FG loops of EhICP2 may be important to facilitate the initial binding of this inhibitor to the battery of CPs present in E. histolytica.