| タイトル | The Crystallization of Canavalin as a Function of pH and NaCl Concentration |
| 著者（英） | Forsythe, Elizabeth L.; Gorti, Sridhar; Pusey, Marc L. |
| 著者所属（英） | NASA Marshall Space Flight Center |
| 発行日 | 2004-01-01 |
| 言語 | eng |
| 内容記述 | We posed the question of what happens to a protein that is known to grow as an n-mer when it is placed in solution conditions where it is monomeric. The trypsin-treated, or cut, form of the protein canavalin (CCAN) has been shown to nucleate and grow crystals as a trimer from neutral to slightly acidic solutions. Under these conditions the solution is composed almost wholly of trimers. The crystalline protein can be readily dissolved by weakly basic solution, which has been proposed to result in a solution that is monomeric. There are three possible outcomes to an attempt at crystallization of the protein under monomeric (high pH) conditions: 1) we will obtain the same crystals as under trimer conditions, but at different protein concentrations governed by the self association equilibria; 2) we will obtain crystals having a different symmetry, based upon a monomeric growth unit; 3) we will not obtain crystals. Obtaining the first result would be indicative that the solution-phase self-association process is critical to the crystal nucleation and growth process. The second result would be less clear, as it may also reflect a pH-dependent shift in the trimer-trimer molecular interactions. The third result, particularly for experiments in the transition pH's between trimeric and monomeric CCAN, would indicate that the monomer does not crystallize, and that solution phase self association is not part of the crystal nucleation and growth path. Results are presented for crystallization experiments of CCAN over the pH 6.4 to 9.6 range. Fluorescence anisotropy, light scattering, and gel filtration experiments show that the solutions are primarily trimers, with association to form larger species occurring as a function of protein concentration. |
| NASA分類 | Inorganic, Organic and Physical Chemistry |
| 権利 | Copyright |
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