High-resolution structures of annexin A5 in a two-dimensional array |
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Institution: | 1. Department of Ultrasound Diagnosis, Tangdu Hospital, Fourth Military Medical University, Xi''an 710038, China;2. Department of Ultrasound Diagnosis, General Hospital of the PLA Rocket Force, Beijing 100088, China;3. Department of Medical Laboratory and Research Center, Tangdu Hospital, Fourth Military Medical University, Xi''an 710038, China;4. Department of Neurology, Xijing Hospital, Fourth Military Medical University, Xi''an 710032, China;5. Department of Biochemistry and Molecular Biology, Fourth Military Medical University, Xi''an 710032, China |
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Abstract: | Annexins are soluble cytosolic proteins that bind to cell membranes. Annexin A5 self-assembles into a two-dimensional (2D) array and prevents cell rupture by attaching to damaged membranes. However, this process is not fully understood at the molecular level. In this study, we determined the crystal structures of annexin A5 with and without calcium (Ca2+) and confirmed the Ca2+-dependent outward motion of a tryptophan residue. Strikingly, the two structures exhibited the same crystal packing and 2D arrangement into a p3 lattice, which agrees well with the results of low-resolution structural imaging. High-resolution structures indicated that a three-fold interaction near the tryptophan residue is important for mediating the formation of the p3 lattice. A hypothesis on the promotion of p3 lattice formation by phosphatidyl serine (PS) is also suggested. This study provides molecular insight into how annexins modulate the physical properties of cell membranes as a function of Ca2+ concentration and the phospholipid composition of the membrane. |
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Keywords: | Annexin Crystal structure Two-dimensional array Membrane rupture |
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