PDBsum entry 2ig3

Oxygen storage/transport

PDB id: 2ig3

Contents

Protein chains

127 a.a. *

Ligands

CYN ×2

ACT ×3

SO4 ×4

HEM ×2

Waters ×93

* Residue conservation analysis

PDB id:

2ig3

Name:

Oxygen storage/transport

Title:

Crystal structure of group iii truncated hemoglobin from campylobacter jejuni

Structure:

Group iii truncated haemoglobin. Chain: a, b. Synonym: group iii truncated hemoglobin. Engineered: yes

Source:

Campylobacter jejuni. Organism_taxid: 197. Gene: ctb. Expressed in: escherichia coli. Expression_system_taxid: 562.

Resolution:

2.15Å R-factor: 0.212 R-free: 0.262

Authors:

M.Nardini,A.Pesce,M.Labarre,P.Ascenzi,M.Guertin,M.Bolognesi

Key ref:

M.Nardini et al. (2006). Structural determinants in the group III truncated hemoglobin from Campylobacter jejuni. J Biol Chem, 281, 37803-37812. PubMed id: 17023416 DOI: 10.1074/jbc.M607254200

Date:

22-Sep-06 Release date: 10-Oct-06

Protein chains

Q0PB48  (TRHBP_CAMJE) -  Group 3 truncated hemoglobin ctb from Campylobacter jejuni subsp. jejuni serotype O:2 (strain ATCC 700819 / NCTC 11168)

Seq: 127 a.a.

Struc: 127 a.a.

DOI no: 10.1074/jbc.M607254200

J Biol Chem 281:37803-37812 (2006)

PubMed id: 17023416

Structural determinants in the group III truncated hemoglobin from Campylobacter jejuni.

M.Nardini, A.Pesce, M.Labarre, C.Richard, A.Bolli, P.Ascenzi, M.Guertin, M.Bolognesi.

ABSTRACT

Truncated hemoglobins (trHbs) constitute a distinct lineage in the globin superfamily, distantly related in size and fold to myoglobin and monomeric hemoglobins. Their phylogenetic analyses revealed that three groups (I, II, and III) compose the trHb family. Group I and II trHbs adopt a simplified globin fold, essentially composed of a 2-on-2 alpha-helical sandwich, wrapped around the heme group. So far no structural data have been reported for group III trHbs. Here we report the three-dimensional structure of the group III trHbP from the eubacterium Campylobacter jejuni. The 2.15-A resolution crystal structure of C. jejuni trHbP (cyano-met form) shows that the 2-on-2 trHb fold is substantially conserved in the trHb group III, despite the absence of the Gly-based sequence motifs that were considered necessary for the attainment of the trHb specific fold. The heme crevice presents important structural modifications in the C-E region and in the FG helical hinge, with novel surface clefts at the proximal heme site. Contrary to what has been observed for group I and II trHbs, no protein matrix tunnel/cavity system is evident in C. jejuni trHbP. A gating movement of His(E7) side chain (found in two alternate conformations in the crystal structure) may be instrumental for ligand entry to the heme distal site. Sequence conservation allows extrapolating part of the structural results here reported to the whole trHb group III.

Selected figure(s)

Figure 2.
FIGURE 2. A comparative view of the trHb fold in the three groups. A, a ribbon stereo view of Cj-trHbP tertiary structure. -Helices are labeled according to the conventional globin fold nomenclature (25). B, structural overlay of group III Cj-trHbP (blue trace) onto group I C. eugametos trHbN (orange trace). C, structural overlay of group III Cj-trHbP (blue trace) onto group II B. subtilis trHbO (yellow trace). The heme groups of each globin are included. All figures were drawn with Molscript (33) and Raster3D (34).

Figure 3.
FIGURE 3. Structure in the heme pocket of Cj-trHbP. A, a stereo view of the heme, of the proximal His(F8), and of the surrounding distal residues contacting the heme and stabilizing the bound cyanide. Hydrogen bonds within the distal residue cluster, including the heme ligand, are indicated with dashed lines. Residue His^46(E7) is shown in the closed and open (magenta) conformations. B, details of the heme distal site, including the C helix (top in the figure) and the E helix; for comparison, the C-E backbone region of group I C. eugametos trHbN (orange) is also displayed.

The above figures are reprinted by permission from the ASBMB: J Biol Chem (2006, 281, 37803-37812) copyright 2006.

Figures were selected by an automated process.