Aleshin, A. E. | bioRxiv Science

bioRxiv2022

Calcium-induced environmental adaptability of the blood protein vitronectin

The adaptability of proteins to their work environments is fundamental for cellular life. Here we describe how the hemopexin-like (HX) domain of the multifunctional blood glycoprotein vitronectin (Vn) binds Ca2+ to adapt to excursions of temperature and shear stress. Using X-ray crystallography and molecular dynamics (MD) simulations, nuclear magnetic resonance (NMR) and differential scanning calorimetry (DSF), we describe how Ca2+ and its flexible hydration shell enable the protein to perform conformational changes, that relay beyond the Ca2+ binding site to alter the number of polar contacts and confer conformational stability. By means of mutagenesis, we identify key residues that cooperate with Ca2+ to promote protein stability, and we show that Ca2+ association confers protection against shear stress, a property that provides conformational advantage for proteins that circulate in the vasculature like Vn. The data reveal a mechanism of adaptation. Significance StatementThe protein vitronectin (Vn) plays important roles in cell adhesion and migration, bone remodeling and immunity. It circulates in blood, but it is also found in the extracellular matrix, and it accumulates with plaques associated with age-related macular degeneration, Alzheimers disease, atherosclerosis and other degenerative disorders. Vn is a calcium-binding protein, and here, we show that calcium helps Vn alter its structure in response to diverse environmental conditions. The results shed light on the way in which Vn adapts to its surroundings. This structural knowledge is important for the development of diagnostic, preventive or therapeutic approaches.

biophysics↗

bioRxiv2020

Structural basis for the association of PLEKHA7 with membrane-embedded phosphatidylinositol lipids

PLEKHA7 (pleckstrin homology domain containing family A member 7) plays key roles in intracellular signaling, cytoskeletal organization and cell adhesion, and is associated with multiple human cancers. The interactions of its pleckstrin homology (PH) domain with membrane phosphatidyl-inositol-phosphate (PIP) lipids, are critical for proper cellular localization and function, and their inhibition is an attractive target for anti-cancer therapy. While structural data can provide insights in this area, little is known about the way in which PLEKHA7 and other PH domains interact with membrane-embedded PIPs. Here we report atomic-resolution structures of the PLEHA7 PH domain and describe the molecular mechanism for its recognition of membrane-bound PIPs. Using X-ray crystallography, nuclear magnetic resonance (NMR), molecular dynamics (MD) simulations, and isothermal titration calorimetry (ITC), we show - in atomic-level detail - that the interaction of PLEKHA7 with PIPs is multivalent and induces PIP clustering. The PIP binding mechanism is distinct from a discrete one-to-one interaction. Our findings reveal a central role of the membrane assembly in mediating protein-PIP association and provide a roadmap for the design of PLEKHA7-PIP inhibitors.

biochemistry↗