title: Unmasking the annexin I interaction from the structure of Apo-S100A11.
abstract: S100A11 is a homodimeric EF-hand calcium binding protein that undergoes a calcium-induced conformational change and interacts with the phospholipid binding protein annexin I to coordinate membrane association. In this work, the solution structure of apo-S100A11 has been determined by NMR spectroscopy to uncover the details of its calcium-induced structural change. Apo-S100A11 forms a tight globular structure having a near antiparallel orientation of helices III and IV in calcium binding site II. Further, helices I and IV, and I and I', form a more closed arrangement than observed in other apo-S100 proteins. This helix arrangement in apo-S100A11 partially buries residues in helices I (P3, E11, A15), III (V55, R58, M59), and IV (A86, C87, S90) and the linker (A45, F46), which are required for interaction with annexin I in the calcium-bound state. In apo-S100A11, this results in a "masked" binding surface that prevents annexin I binding but is uncovered upon calcium binding.
authors.affiliation: Department of Biochemistry, The University of Western Ontario, London, Ontario N6A 5C1, Canada.
authors.forename: Anne C
authors.initials: AC
authors.lastname: Dempsey
authors.forename: Michael P
authors.initials: MP
authors.lastname: Walsh
authors.forename: Gary S
authors.initials: GS
authors.lastname: Shaw
mesh_terms: D017305:Annexin A1 / Q000737:chemistry / Q000378:metabolism*; D019281:Dimerization; D019906:Nuclear Magnetic Resonance, Biomolecular; D009418:S100 Proteins / Q000737:chemistry / Q000378:metabolism*
chemical_list: D017305:Annexin A1; D009418:S100 Proteins; C072337:S100A11 protein, human