PDBsum entry 1dk0

Transport protein

PDB id: 1dk0

Contents

Protein chains

173 a.a. *

Ligands

HEM ×2

Waters ×222

* Residue conservation analysis

PDB id:

1dk0

Name:

Transport protein

Title:

Crystal structure of the hemophore hasa from serratia marcescens crystal form p2(1), ph8

Structure:

Heme-binding protein a. Chain: a, b. Synonym: hasa. Engineered: yes

Source:

Serratia marcescens. Organism_taxid: 615. Expressed in: escherichia coli. Expression_system_taxid: 562

Biol. unit:

Dimer (from PQS)

Resolution:

1.77Å R-factor: 0.175 R-free: 0.213

Authors:

P.Arnoux,R.Haser,N.Izadi-Pruneyre,A.Lecroisey,M.Czjzek

Key ref:

P.Arnoux et al. (2000). Functional aspects of the heme bound hemophore HasA by structural analysis of various crystal forms. Proteins, 41, 202-210. PubMed id: 10966573 DOI: 10.1002/1097-0134(20001101)41:2<202::AID-PROT50>3.0.CO;2-8

Date:

06-Dec-99 Release date: 27-Dec-00

Protein chains

Q54450  (HASA_SERMA) -  Hemophore HasA from Serratia marcescens

Seq: 188 a.a.

Struc: 173 a.a.

Enzyme reactions

• Enzyme class: E.C.?

DOI no: 10.1002/1097-0134(20001101)41:2<202::AID-PROT50>3.0.CO;2-8

Proteins 41:202-210 (2000)

PubMed id: 10966573

Functional aspects of the heme bound hemophore HasA by structural analysis of various crystal forms.

P.Arnoux, R.Haser, N.Izadi-Pruneyre, A.Lecroisey, M.Czjzek.

ABSTRACT

The protein HasA from the Gram negative bacteria Serratia marcescens is the first hemophore to be described at the molecular level. It participates to the shuttling of heme from hemoglobin to the outer membrane receptor HasR, which in turn releases it into the bacterium. HasR alone is also able to take up heme from hemoglobin but synergy with HasA increases the efficiency of the system by a factor of about 100. This iron acquisition system allows the bacteria to survive with hemoglobin as the sole iron source. Here we report the structures of a new crystal form of HasA diffracting up to 1.77A resolution as well as the refined structure of the trigonal crystal form diffracting to 3.2A resolution. The crystal structure of HasA at high resolution shows two possible orientations of the heme within the heme-binding pocket, which probably are functionally involved in the heme-iron acquisition process. The detailed analysis of the three known structures reveals the molecular basis regulating the relative affinity of the heme/hemophore complex.

Selected figure(s)

Figure 3.
Figure 3. Illustration of the two possibilities of inserting the heme into the protein moiety assessed by high resolution X-ray crystallography: A: electron density maps: 3F[o]-2F[c] map contoured at 1 (blue) and F[o]-F[c] map contoured at -2.5 (red) and +2.5 (green), B: the corresponding two orientations of the heme.

Figure 4.
Figure 4. Schematic representation of the heme environment. In the hemophore structure the most exposed heme edge is on side b (side defined in Fig. 5). Each propionate is involved in several hydrogen bonds with the protein, in this way forming a propionate zip.

The above figures are reprinted by permission from John Wiley & Sons, Inc.: Proteins (2000, 41, 202-210) copyright 2000.

Figures were selected by the author.