Protein crystal lattices are dynamic assemblies: the role of conformational entropy in the protein condensed phase

The FUSION protein crystallization screen

The success and speed of atomic structure determination of biological macromolecules by X-ray crystallography depends critically on the availability of diffraction-quality crystals. However, the process of screening crystallization conditions often consumes large amounts of sample and time. An innovative protein crystallization screen formulation called FUSION has been developed to help with the production of useful crystals. The concept behind the formulation of FUSION was to combine the most efficient components from the three MORPHEUS screens into a single screen using a systematic approach. The resulting formulation integrates 96 unique combinations of crystallization additives. Most of these additives are small molecules and ions frequently found in crystal structures of the Protein Data Bank (PDB), where they bind proteins and complexes. The efficiency of FUSION is demonstrated by obtaining high yields of diffraction-quality crystals for seven different test proteins. In the process, two crystal forms not currently in the PDB for the proteins α-amylase and avidin were discovered.

High mobility of lattice molecules and defects during the early stage of protein crystallization

Protein crystals are expected to be useful not only for their molecular structure analysis but also as functional materials due to their unique properties. Although the generation and the propagation of defects during crystallization play critical roles in the final properties of protein crystals, the dynamics of these processes are poorly understood. By time-resolved liquid-cell transmission electron microscopy, we observed that nanosized crystal defects are surprisingly mobile during the early stages of the crystallization of a lysozyme as a model protein. This highly dynamic behavior of defects reveals that the lattice molecules are mobile throughout the crystal structure. Moreover, the disappearance of the defects indicated that intermolecular bonds can break and reform rapidly with little energetic cost, as reported in theoretical studies. All these findings are in marked contrast to the generally accepted notion that crystal lattices are rigid with very limited mobility of individual lattice molecules.

Comment on the article 'Protein crystal lattices are dynamic assemblies: the role of conformational entropy in the protein condensed phase'

A comment is given on Dimova & Devedjiev [IUCrJ (2018), 5, 130-140].

Response to comment on 'Protein crystal lattices are dynamic assemblies: the role of conformational entropy in the protein condensed phase'

A response is given to Nespolo's comment [IUCrJ (2018), 5, https://doi.org/10.1107/S2052252518006267] about the usage of the the term 'crystal lattice' in Dimova & Devedjiev [IUCrJ (2018), 5, 130-140].