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Psb27 is a highly conserved component of photosystem II. The three-dimensional structure has a well-defined helical core, composed of four helices arranged in a right-handed up-down-up-down fold, with a less ordered region of the structure located at the N-terminus. The position of conserved residues on the surface suggests conserved functional roles for distinct interconnected features encompassing a P-phi-P loop, a polar patch spanning helices alpha3 and alpha4, and the N-terminal sequence.