Crystallization

Fiber proteins can in principle be crystallized using the same strategies as globular proteins, trying different precipitants, pHs, additives, and temperatures. The virus-binding regions in fiber proteins may, however, in the absence of the rest of the virus or bacteriophage, be unfolded and lead to a specific aggregation, hindering crystallization. Furthermore, because they often have specific regions where the fiber is bent or kinked, this can lead to lower success rates in crystallization and, in the case of successful structural determination, regions that are disordered in the crystallographic electron density. The identification of a stable domain, eliminating some or all of the binding regions,

Fig. 2. Schematic drawing of adenovirus (left) and structure of adenovirus type 2 fiber stable fragment (right). The head domain, linker region, and shaft repeats are labeled. In the full-length fiber proteins up to 22 repeats are present. The part of the fiber of which the structure is shown is boxed. The shown adenovirus particle is about 80 nm wide (not counting the fibers, which can measure up to 35 nm each), and the part of the structure shown is about 10 nm long. The figures were produced using Molscript (56) and atomic coordinates publicly available from the PDB protein structure database (http://www.rcsb.org). One of the chains is shown in black and the other two in gray. The PDB code for the adenovirus type 2 stable fragment is 1QIU.

Fig. 2. Schematic drawing of adenovirus (left) and structure of adenovirus type 2 fiber stable fragment (right). The head domain, linker region, and shaft repeats are labeled. In the full-length fiber proteins up to 22 repeats are present. The part of the fiber of which the structure is shown is boxed. The shown adenovirus particle is about 80 nm wide (not counting the fibers, which can measure up to 35 nm each), and the part of the structure shown is about 10 nm long. The figures were produced using Molscript (56) and atomic coordinates publicly available from the PDB protein structure database (http://www.rcsb.org). One of the chains is shown in black and the other two in gray. The PDB code for the adenovirus type 2 stable fragment is 1QIU.

greatly aids in obtaining diffracting crystals. As with globular proteins, important for the success of crystallization is purity, conformational homogeneity, and the ability to obtain the protein in reasonable amounts (upward from about 0.5 mg) and at relatively high concentrations (5-50 mg/mL).

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