Structure determination of a cocaine hydrolytic antibody from a pseudomerohedrally twinned crystal

Abstract

Few examples of pseudomerohedrally twinned macromolecular crystals have been described in the literature. This unusual phenomenon arises when a fortuitous unit-cell geometry makes it possible for twinning to occur in a space group that ordinarily does not allow twinning. Here, the crystallization, structure determination and re®nement of the cocaine hydrolytic antibody 15A10 at 2.35 A Ê resolution are described. The crystal belongs to space group P2 1 , with two molecules in the asymmetric unit and unit-cell parameters a = 37.5, b = 108.4, c = 111.3 A Ê and fortuitously near 90; the re®ned twinning fraction is = 0.43. Interestingly, the noncrystallographic symmetry (NCS) and twin operators are nearly parallel, which appears to be a relatively frequent situation in protein crystals twinned by merohedry or pseudomerohedry.

Crystal Structure of Nicotinic Acid Mononucleotide Adenylyltransferase from Pseudomonas aeruginosa in its Apo and Substrate-complexed Forms Reveals a Fully Open Conformation

“…These twinned R values probably underestimate the true crystallographic R values to some extent. 16 The NaMN-bound model includes 848 residues of four independent monomers in the asymmetric unit (residues 2-213 in each monomer), four citrate ions, four NaMN molecules, and 813 water molecules (Figure 1(b)). The ATP-bound model includes 420 residues of two independent monomers in the asymmetric unit (residues 2-211 in each monomer), two ATP molecules, 304 water molecules, and a magnesium ion (Figure 1(c)).…”

Crystal Structure of Two Anti-Porphyrin Antibodies with Peroxidase Activity

“…Fab 13G10 crystallized with one molecule in the asymmetric unit, whereas the crystals of Fab 14H7 contained eight Fab molecules in the asymmetric unit and were pseudomerohedrally twinned [42], [43], [44]. Twinning was detected using the xtriage program included in PHENIX [25].…”

Crystal Structure of the Spindle Assembly Checkpoint Protein Bub3

“…SHELXL allows simultaneous refinement of the structure and the twinning fraction. [32][33][34] The resulting sigma weighted maps revealed clear differences in the electron density between the two molecules in the asymmetric unit, especially in the flexible loop regions.…”