Emerging from pseudo-symmetry: the redetermination of human carbonic anhydrase II in monoclinicP2₁with a doubledaaxis

Abstract

PDB Reference: human carbonic anhydrase II, 3mwo.The crystal structure of human carbonic anhydrase II in the monoclinic P2 1 space group with a doubled a axis from that of the usually observed unit cell has recently been reported, with one of the two molecules in the asymmetric unit demonstrating rotational disorder [Robbins et al. (2010), Acta Cryst. D66, 628-634]. The structure has been redetermined, with the coordinates of both pseudosymmetrically related molecules in the crystallographic asymmetric unit translated by x 0 = x AE 1/4, and no rotational disorder is observed. This corresponds to a different choice of how the four molecules in the unit cell should be grouped into pairs that represent a single asymmetric unit.

A challenging interpretation of a hexagonally layered protein structure

“…Unexpectedly, however, the P2 1 space-group symmetry of the simpler crystal form was also broken under the most obvious choice of origin for the doubled unit cell, leading to apparent disorder. The correct structure, which was fully ordered, was obtained in retrospect when it was found that shifting the origin of the doubled unit cell led to recovery of the required symmetry elements in P2 1 (Robbins et al, 2010a). Likewise, in our study, the shifting of a second hexagonal layer relative to the first layer breaks the P6 symmetry that would have been present in a single layer, leaving what appears to be P3 symmetry under the original choice of unit cell (Fig.…”

Thermodynamic, kinetic, and structural parameterization of human carbonic anhydrase interactions toward enhanced inhibitor design

“…High-resolution crystal structures of CA II appeared later and helped to understand the water network in the active site (Fisher et al, 2007a;Avvaru et al, 2010b). There was also some variability in crystal forms of CA II, first mentioned by Robbins et al (2010).…”

“…There was also some variability in crystal forms of CA II, first mentioned by Robbins et al . (2010).…”

Partial rotational lattice order–disorder in stefin B crystals

“…Pletnev and coworkers named this disorder a 'rotational order-disorder structure'. In addition, the structure of human carbonic anhydrase was first identified as a rotational order-disorder structure (Robbins et al, 2010a); however, this identification was later corrected and refined as a structure with an alternative selection of molecules in the asymmetric unit (Robbins et al, 2010b).…”