Enhanced crystallization of the Cys18 to Ser mutant of bovine gammaB crystallin.Asherie, N., Pande, J., Pande, A., Zarutskie, J.A., Lomakin, J., Lomakin, A., Ogun, O., Stern, L.J., King, J., Benedek, G.B.
(2001) J.Mol.Biol. 314: 663-669
- PubMed: 11733987
- DOI: 10.1006/jmbi.2001.5155
- PubMed Abstract:
- X-ray analysis of the eye lens protein Gamma-II Crystallin at 1.9 Angstrom Resolution
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(1983) J.Mol.Biol. 170: 175
- The molecular structure and stability of the eye lens: X-Ray Analysis of Gamma-Crystallin II
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(1981) Nature 289: 771
- X-Ray Studies of the Lens Specific Proteins, the Crystallins
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- Structure of the Bovine Eye Lens Protein Gamma-B (Gamma-II)-Crystallin at 1.47 Angstroms
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(1993) Acta Crystallogr.,Sect.D 49: 223
The cysteine residues of the gamma crystallins, a family of ocular lens proteins, are involved in the aggregation and phase separation of these proteins. Both these phenomena are implicated in cataract formation. We have used bovine gammaB crystallin ...
The cysteine residues of the gamma crystallins, a family of ocular lens proteins, are involved in the aggregation and phase separation of these proteins. Both these phenomena are implicated in cataract formation. We have used bovine gammaB crystallin as a model system to study the role of the individual cysteine residues in the aggregation and phase separation of the gamma crystallins. Here, we compare the thermodynamic and kinetic behavior of the recombinant wild-type protein (WT) and the Cys18 to Ser (C18S) mutant. We find that the solubilities of the two proteins are similar. The kinetics of crystallization, however, are different. The WT crystallizes slowly enough for the metastable liquid-liquid coexistence to be easily observed. C18S, on the other hand, crystallizes rapidly; the metastable coexisting liquid phases of the pure mutant do not form. Nevertheless, the coexistence curve of C18S can be determined provided that crystallization is kinetically suppressed. In this way we found that the coexistence curve coincides with that of the WT. Despite the difference in the kinetics of crystallization, the two proteins were found to have the same crystal forms and almost identical X-ray structures. Our results demonstrate that even conservative point mutations can bring about dramatic changes in the kinetics of crystallization. The implications of our findings for cataract formation and protein crystallization are discussed.
Department of Physics, Center for Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge 02139-4307, USA.