Tetragonal Crystal Form (tetragonal + crystal_form)

Distribution by Scientific Domains

Selected Abstracts

Analysis of multiple crystal forms of Bacillus subtilis BacB suggests a role for a metal ion as a nucleant for crystallization

M. Rajavel
Bacillus subtilis BacB is an oxidase that is involved in the production of the antibiotic bacilysin. This protein contains two double-stranded ,-helix (cupin) domains fused in a compact arrangement. BacB crystallizes in three crystal forms under similar crystallization conditions. An interesting observation was that a slight perturbation of the crystallization droplet resulted in the nucleation of a different crystal form. An X-ray absorption scan of BacB suggested the presence of cobalt and iron in the crystal. Here, a comparative analysis of the different crystal forms of BacB is presented in an effort to identify the basis for the different lattices. It is noted that metal ions mediating interactions across the asymmetric unit dominate the different packing arrangements. Furthermore, a normalized B -factor analysis of all the crystal structures suggests that the solvent-exposed metal ions decrease the flexibility of a loop segment, perhaps influencing the choice of crystal form. The residues coordinating the surface metal ion are similar in the triclinic and monoclinic crystal forms. The coordinating ligands for the corresponding metal ion in the tetragonal crystal form are different, leading to a tighter packing arrangement. Although BacB is a monomer in solution, a dimer of BacB serves as a template on which higher order symmetrical arrangements are formed. The different crystal forms of BacB thus provide experimental evidence for metal-ion-mediated lattice formation and crystal packing. [source]

Structure of the X (ADRP) domain of nsp3 from feline coronavirus

Justyna A. Wojdyla
The structure of the X (or ADRP) domain of a pathogenic variant of feline coronavirus (FCoV) has been determined in tetragonal and cubic crystal forms to 3.1 and 2.2,┼ resolution, respectively. In the tetragonal crystal form, glycerol-3-phosphate was observed in the ADP-ribose-binding site. Both crystal forms contained large solvent channels and had a solvent content of higher than 70%. Only very weak binding of this domain to ADP-ribose was detected in vitro. However, the structure with ADP-ribose bound was determined in the cubic crystal form at 3.9,┼ resolution. The structure of the FCoV X domain had the expected macro-domain fold and is the first structure of this domain from a coronavirus belonging to subgroup 1a. [source]

Structure of Escherichia coli pyridoxine 5,-phosphate oxidase in a tetragonal crystal form: insights into the mechanistic pathway of the enzyme

Faik N. Musayev
Escherichia coli pyridoxine 5,-phosphate oxidase (ePNPOx) catalyzes the terminal step in the biosynthesis of pyridoxal 5,-şphosphate (PLP) by the FMN oxidation of pyridoxine 5,-şphosphate (PNP) or pyridoxamine 5,-phosphate (PMP), forming FMNH2 and H2O2. The crystal structure of ePNPOx is reported in a tetragonal unit cell at 2.6,┼ resolution. The three-dimensional fold of this structure is very similar to those of the E. coli and human enzymes that crystallized in trigonal and monoclinic unit cells. However, unlike the previous structures, the tetragonal structure shows major disorder in one of the two subunit domains that has opened up both the active site and a putative tunnel. Comparison of these structures gives an insight into the mechanistic pathway of PNPOx: from the resting enzyme with no substrate bound, to the initial binding of the substrate at the active site, to the catalytic stage and to the release of the catalytic product from the active site. [source]

Crystallization and preliminary characterization of the Thermus thermophilus RNA helicase Hera C-terminal domain

Markus G. Rudolph
Heat-resistant RNA-dependent ATPase (Hera) from Thermus thermophilus is a DEAD-box RNA helicase. Two constructs encompassing the second RecA-like domain and the C-terminal domain of Hera were overproduced in Escherichia coli and purified to homogeneity. Single crystals of both Hera constructs were obtained in three crystal forms. A tetragonal crystal form belonged to space group P41212, with unit-cell parameters a = 65.5, c = 153.0,┼, and contained one molecule per asymmetric unit. Two orthorhombic forms belonged to space group P212121, with unit-cell parameters a = 62.8, b = 70.9, c = 102.3,┼ (form I) and a = 41.6, b = 67.6, c = 183.5,┼ (form II). Both orthorhombic forms contained two molecules per asymmetric unit. All crystals diffracted X-rays to beyond 3,┼ resolution, but the tetragonal data sets displayed high Wilson B values and high mean |E2, 1| values, indicating potential disorder and anisotropy. The tetragonal crystal was phased by MAD using a single selenium site. [source]

Reductive methylation to improve crystallization of the putative oxidoreductase Rv0765c from Mycobacterium tuberculosis

Wilko Rauert
Rv0765c from Mycobacterium tuberculosis was cloned and heterologously expressed in Escherichia coli. It was purified using affinity and size-exclusion chromatographic techniques and crystallized. The native protein crystallized in a hexagonal crystal form which diffracted to 7,┼ resolution. In an attempt to improve the quality of the Rv0765c crystals, the protein was modified by reductive methylation using dimethylaminoborane and formaldehyde. The modified protein crystallized under different conditions in a tetragonal crystal form, from which diffraction data could be collected to a resolution of 3.2,┼. In both crystal forms of Rv0765c, the asymmetric unit contained two copies of the protein molecule. [source]