PDBsum entry 3fxe

Unknown function

PDB id: 3fxe

Contents

Protein chains

48 a.a. *

56 a.a. *

Waters ×33

* Residue conservation analysis

PDB id:

3fxe

Name:

Unknown function

Title:

Crystal structure of interacting domains of icmr and icmq (seleno- derivative)

Structure:

Protein icmq. Chain: a. Fragment: unp residues 1-57. Engineered: yes. Protein icmr. Chain: b. Fragment: unp residues 23-95. Engineered: yes. Mutation: yes

Source:

Legionella pneumophila. Organism_taxid: 400673. Strain: corby. Gene: icmq, lpc_2899. Expressed in: escherichia coli. Expression_system_taxid: 562. Legionella pneumophila subsp. Pneumophila str. Philadelphia 1. Organism_taxid: 272624.

Resolution:

2.20Å R-factor: 0.230 R-free: 0.250

Authors:

S.Raychaudhury,C.W.Akey,J.F.Head

Key ref:

S.Raychaudhury et al. (2009). Structure and Function of Interacting IcmR-IcmQ Domains from a Type IVb Secretion System in Legionella pneumophila. Structure, 17, 590-601. PubMed id: 19368892 DOI: 10.1016/j.str.2009.02.011

Date:

20-Jan-09 Release date: 28-Apr-09

Protein chain

No UniProt id for this chain

Struc: 48 a.a.

Protein chain

Q5ZYC9  (Q5ZYC9_LEGPH) -  IcmR from Legionella pneumophila subsp. pneumophila (strain Philadelphia 1 / ATCC 33152 / DSM 7513)

Seq: 120 a.a.

Struc: 56 a.a.*

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

DOI no: 10.1016/j.str.2009.02.011

Structure 17:590-601 (2009)

PubMed id: 19368892

Structure and Function of Interacting IcmR-IcmQ Domains from a Type IVb Secretion System in Legionella pneumophila.

S.Raychaudhury, J.D.Farelli, T.P.Montminy, M.Matthews, J.F.Ménétret, G.Duménil, C.R.Roy, J.F.Head, R.R.Isberg, C.W.Akey.

ABSTRACT

During infection, Legionella pneumophila creates a replication vacuole within eukaryotic cells and this requires a Type IVb secretion system (T4bSS). IcmQ plays a critical role in the translocase and associates with IcmR. In this paper, we show that the N-terminal domain of IcmQ (Qn) mediates self-dimerization, whereas the C-terminal domain with a basic linker promotes membrane association. In addition, the binding of IcmR to IcmQ prevents self-dimerization and also blocks membrane permeabilization. However, IcmR does not completely block membrane binding by IcmQ. We then determined crystal structures of Qn with the interacting region of IcmR. In this complex, each protein forms an alpha-helical hairpin within a parallel four-helix bundle. The amphipathic nature of helices in Qn suggests two possible models for membrane permeabilization by IcmQ. The Rm-Qn structure also suggests how IcmR-like proteins in other L. pneumophila species may interact with their IcmQ partners.

Selected figure(s)

Figure 4.
Figure 4. Structure of an Rm-Qn Four-Helix Bundle
(A) A rotation series of the Rm-Qn four-helix bundle is presented with the molecules displayed as ribbons. This structure is from the derivative crystals.
(B) Nonpolar side chains in the Rm-Qn interface are shown as solid spheres and are color coded for those from Qn (blue) and from Rm (tan).
(C) Side chains in the Rm-Qn interface are shown as stick models with CPK colors and are labeled.
(D) A top view is shown of the Rm-Qn four-helix bundle with α helices displayed as ribbons and side chains as CPK stick models. The figure was made with Chimera.

Figure 6.
Figure 6. Qn α Helices are Amphipathic and Show a Charge Segregation
(A) Qn α helices are shown in the context of the Rm-Qn dimer (left) and dissected out from the helix bundle (center and right). The Qn α helices are amphipathic with a hydrophobic face (green arrows) and charged faces (blue arrow for basic and red arrow for acidic).
(B) Helix wheel diagrams for the two Qn α helices show the charge segregation between the two α helices.
(C) A possible model is shown for the Qn-Qn four-helix bundle that may mediate IcmQ dimerization.

The above figures are reprinted by permission from Cell Press: Structure (2009, 17, 590-601) copyright 2009.

Figures were selected by the author.

Author's comment

The middle domain of IcmR in the hypervariable FIR family, probably acts like a chaperone and binds tightly to the N-terminal domain of IcmQ to form a four helix bundle. These proteins are novel to the Type 4b secretion system and are required for L. pneumophila infectivity.