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Structure and lipid binding properties of the kindlin-3 pleckstrin homology domain

DOI: 10.1042/BCJ20160791 DOI Help

Authors: Tao Ni (University of Oxford) , Antreas Kalli (University of Oxford) , Fiona Naughton (University of Oxford) , Luke Yates (University of Oxford) , Omar Naneh (National Institute of Chemistry, Slovenia) , Mirijam Kozorog (National Institute of Chemistry, Slovenia) , Gregor Anderluh (University of Ljubljana) , Mark Sansom (University of Oxford) , Robert Gilbert (University of Oxford)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Biochemical Journal

State: Published (Approved)
Published: December 2016

Abstract: Kindlins co-activate integrins alongside talin. They possess, like talin, a FERM domain comprising F0-F3 subdomains, but with a pleckstrin homology (PH) domain inserted in the F2 subdomain that enables membrane association. We present the crystal structure of murine kindlin-3 PH domain determined at 2.23Å resolution and characterise its lipid binding using biophysical and computational approaches. Molecular dynamics (MD) simulations suggest flexibility in the PH domain loops connecting β-strands forming the putative phosphatidylinositol phosphate (PtdInsP) binding site. Simulations with PtdInsP-containing bilayers reveal that the PH domain associates with PtdInsP molecules mainly via the positively charged surface presented by the β1-β2 loop and that it binds with somewhat higher affinity to PtdIns(3,4,5)P3 compared to PtdIns(4,5)P2. Surface plasmon resonance (SPR) with lipid headgroups immobilised and the PH domain as analyte indicate affinities of 300 μM for PtdIns(3,4,5)P3 and 1mM for PtdIns(4,5)P2. In contrast, SPR studies with immobilised PH domain and lipid nanodiscs as analyte show affinities of 0.40 µM for PtdIns(3,4,5)P3 and no affinity for PtdIns(4,5)P2 when the inositol phosphate constitutes 5% of the total lipids (~5 molecules per nanodisc). Reducing the PtdIns(3,4,5)P3 composition to 1% abolishes nanodisc binding to the PH domain, as does site-directed mutagenesis of two lysines within the β1-β2 loop. Binding of PtdIns(3,4,5)P3 by a canonical PH domain, Grp1, is not similarly influenced by SPR experimental design. These data suggest a role for PtdIns(3,4,5)P3 clustering in the binding of some PH domains and not others, highlighting the importance lipid mobility and clustering for the biophysical assessment of protein-membrane interactions.

Journal Keywords: PH domain; lipid clustering; X-ray crystallography; molecular dynamics; surface plasmon resonance

Subject Areas: Biology and Bio-materials

Instruments: I24-Microfocus Macromolecular Crystallography

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