Crystal Structures of Sodium-Bound Annexin A4

概要

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Annexin A4 (Anx4) possesses four repeat domains with one Ca2+-binding site (CBS) in each domain. In this study, we resolved two crystal structures of the Na+-bound form at high resolution (1.58 and 1.35 Å). This is the first report that Anx4 binds the Na+ ion in CBSs. Electron density maps, valence screening, and atomic absorbance spectrometry confirmed that Anx4 bound the Na+ ion. One structure (1.58 Å) bound the Na+ ion in CBS I, whereas another structure (1.35 Å) bound the Na+ ion in CBS II and CBS III. We compared the two Na+-bound forms by superimposing their Cα traces. The Cα atoms of CBS III largely moved by coordination of the Na+ ion. In the Cα atoms of CBS I, however, little change resulted from Na+-coordination. Only the side chain of Glu71 was moved by Na+-coordination in CBS I. These results indicate that Anx4 also binds not only Ca2+ but also Na+ ion in the CBS.
社団法人日本農芸化学会の論文
2009-10-23