title: Low-resolution ab initio phasing of Sarcocystis muris lectin SML-2.
abstract: Structural analysis of the lectin SML-2 faced difficulties when applying standard crystallographic phasing methods. The connectivity-based ab initio phasing method allowed the computation of a 16 A resolution Fourier synthesis and the derivation of primary structural information. It was found that SML-2 crystals have three dimers in the asymmetric part of the unit cell linked by a noncrystallographic symmetry close to translation by (0, 0, 1/3). A clear identification of the noncrystallographic twofold axis explains the space-group transformation from the primitive P2(1)2(1)2(1) to the C-centred C222(1) observed during annealing procedures within an N(2) cryostream for cocrystals of SML-2 and galactose. Related packing considerations predict a possible arrangement of SML-2 molecules in a tetragonal unit cell. Multiple noncrystallographic symmetries and crystal forms provide a basis for further image improvements.
authors.affiliation: Macromolecular Structure and Interactions, Max-Delbrück-Centrum für Molekulare Medizin, Robert-Rössle-Strasse 10, D-13092 Berlin, Germany.
authors.forename: Jürgen J
authors.initials: JJ
authors.lastname: Müller
authors.forename: Natalia L
authors.initials: NL
authors.lastname: Lunina
authors.forename: Alexandre
authors.initials: A
authors.lastname: Urzhumtsev
authors.forename: Edgar
authors.initials: E
authors.lastname: Weckert
authors.forename: Udo
authors.initials: U
authors.lastname: Heinemann
authors.forename: Vladimir Y
authors.initials: VY
authors.lastname: Lunin
mesh_terms: D000818:Animals; D018360:Crystallography, X-Ray; D019281:Dimerization; D005583:Fourier Analysis; D005690:Galactose / Q000737:chemistry; D037161:Galectins / Q000737:chemistry*; D008958:Models, Molecular; D010984:Platinum / Q000737:chemistry; D015800:Protozoan Proteins / Q000737:chemistry*; D012522:Sarcocystis
chemical_list: D037161:Galectins; D015800:Protozoan Proteins; D010984:Platinum; D005690:Galactose