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Quadruple space‐group ambiguity owing to rotational and translational noncrystallographic symmetry in human liver fructose‐1,6‐bisphosphatase
Author(s) -
Ruf Armin,
Tetaz Tim,
Schott Brigitte,
Joseph Catherine,
Rudolph Markus G.
Publication year - 2016
Publication title -
acta crystallographica section d
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.374
H-Index - 138
ISSN - 2059-7983
DOI - 10.1107/s2059798316016715
Subject(s) - crystallography , chemistry , space group , crystal structure , physics , quantum mechanics , x ray crystallography , diffraction
Fructose‐1,6‐bisphosphatase (FBPase) is a key regulator of gluconeogenesis and a potential drug target for type 2 diabetes. FBPase is a homotetramer of 222 symmetry with a major and a minor dimer interface. The dimers connected via the minor interface can rotate with respect to each other, leading to the inactive T‐state and active R‐state conformations of FBPase. Here, the first crystal structure of human liver FBPase in the R‐state conformation is presented, determined at a resolution of 2.2 Å in a tetragonal setting that exhibits an unusual arrangement of noncrystallographic symmetry (NCS) elements. Self‐Patterson function analysis and various intensity statistics revealed the presence of pseudo‐translation and the absence of twinning. The space group is P 4 1 2 1 2, but structure determination was also possible in space groups P 4 3 2 1 2, P 4 1 22 and P 4 3 22. All solutions have the same arrangement of three C 2 ‐symmetric dimers spaced by 1/3 along an NCS axis parallel to the c axis located at (1/4, 1/4, z ), which is therefore invisible in a self‐rotation function analysis. The solutions in the four space groups are related to one another and emulate a body‐centred lattice. If all NCS elements were crystallographic, the space group would be I 4 1 22 with a c axis three times shorter and a single FBPase subunit in the asymmetric unit. I 4 1 22 is a minimal, non‐isomorphic supergroup of the four primitive tetragonal space groups, explaining the space‐group ambiguity for this crystal.