4EYY

Crystal Structure of the IcmR-IcmQ complex from Legionella pneumophila

Summary for 4EYY

• Entry DOI: 10.2210/pdb4eyy/pdb
• Related: 3FXD 3FXE
• Descriptor: IcmR, IcmQ (3 entities in total)
• Functional Keywords: protein heterodimer, adprt-like fold, nad-binding domain, protein binding
• Biological source: Legionella pneumophila subsp. pneumophila; More
• Total number of polymer chains: 2
• Total formula weight: 34475.94

Authors

Farelli, J.D.,Gumbart, J.,Akey, I.V.,Amyot, W.,Hempstead, A.D.,Head, J.F.,McKnight, C.J.,Isberg, R.R.,Akey, C.W. (deposition date: 2012-05-02, release date: 2013-05-22, Last modification date: 2024-02-28)

Primary citation

Farelli, J.D.,Gumbart, J.C.,Akey, I.V.,Hempstead, A.,Amyot, W.,Head, J.F.,McKnight, C.J.,Isberg, R.R.,Akey, C.W.
IcmQ in the Type 4b secretion system contains an NAD+ binding domain.
Structure, 21:1361-1373, 2013

PubMed Abstract: A Type 4b secretion system (T4bSS) is required for Legionella growth in alveolar macrophages. IcmQ associates with IcmR, binds to membranes, and has a critical role in the T4bSS. We have now solved a crystal structure of IcmR-IcmQ to further our understanding of this complex. This structure revealed an amphipathic four-helix bundle, formed by IcmR and the N-terminal domain of IcmQ, which is linked to a novel C-terminal domain of IcmQ (Qc) by a linker helix. The Qc domain has structural homology with ADP ribosyltransferase domains in certain bacterial toxins and binds NAD(+) with a dissociation constant in the physiological range. Structural homology and molecular dynamics were used to identify an extended NAD(+) binding site on Qc, and the resulting model was tested by mutagenesis and binding assays. Based on the data, we suggest that IcmR-IcmQ binds to membranes, where it may interact with, or perhaps modify, a protein in the T4bSS when NAD(+) is bound.

PubMed: 23850453
DOI: 10.1016/j.str.2013.05.017

Experimental method

X-RAY DIFFRACTION (2.4 Å)