'Hot' macromolecular crystals

Abstract

Transcriptional regulator protein TM1030 from the hyperthermophile Thermotoga maritima, as well as its complex with DNA, was crystallized at a wide range of temperatures. Crystallization plates were incubated at 4, 20, 37 and 50° C over 3 weeks. The best crystals of TM1030 in complex with DNA were obtained at 4, 20 and 37° C, while TM1030 alone crystallized almost equally well in all temperatures. The crystals grown at different temperatures were used for X-ray diffraction experiments and their structures were compared. Surprisingly, the models of TM1030 obtained from crystals grown at different temperatures are similar in quality. While there are some examples of structures of proteins grown at elevated temperatures in the PDB, these temperatures appear to be underrepresented. Our studies show that crystals of some proteins may be grown and are stable at broad range of temperatures. We suggest that crystallization experiments at elevated temperatures could be used as a standard part of the crystallization protocol.

Figure 1

The Se-Met derivative of TM1030 crystallized at different temperatures. All pictures were recorded at similar magnification and grown from the same solution (# 95 of Hampton Research’s Index Screen).

Figure 2

Crystals of the TM1030:DNA complex obtained at different temperatures. A) PCSS #61, 20° C; B) PCSS #61, 37° C; C) PCSS #61, 50° C; D) PCSS #35, 20° C; E) PCSS #35, 37° C; F) PCSS #33, 50° C. All pictures were recorded at similar magnification levels.

Figure 3

Percentage of PDB deposits with a non-empty value for the _exptl_crystal_grow.temp data item (reported temperature of crystallization or T_c) in the mmCIF representation of each structure, grouped by the year of deposition. The gray portion of each bar represents the percentage of structures where 273K ≤ T_c ≤ 373K, and the white portion represents the percentage of structures where T_c lay outside this range.

Figure 4

Histograms of the reported T_c for all structures that reported that parameter to the PDB (upper graph; 31884 structures) or were recorded in the BMCD (lower graph; 8587). On both graphs, the boxes marked * collect all structures with reported T_c < 0° C. The boxes marked ** collect all structures with reported T_c ≥ 38° C (311 K).