Crystallographic titration of cubic insulin crystals: pH affects GluB13 switching and sulfate binding.Diao, J.
(2003) Acta Crystallogr D Biol Crystallogr 59: 670-676
- PubMed: 12657786
- DOI: https://doi.org/10.1107/s0907444903002208
- Primary Citation of Related Structures:
1B17, 1B18, 1B19, 1B2A, 1B2B, 1B2C, 1B2D, 1B2E, 1B2F, 1B2G
- PubMed Abstract:
Structures of porcine insulin crystals soaked in 1 M sodium sulfate at pH 5.00, 5.53, 5.80, 6.00, 6.16, 6.26, 6.35, 6.50, 6.98 and 9.00 have been determined at between 1.7 and 1.9 A resolution. GluB13 exhibits a single conformation at pH = 5.80, two conformations between pH 6.00 and 6.98 and a single conformation at pH 9.00. Between pH 6.00 and 6.98, the conformation of GluB13 switches from one rotamer to another rotamer. Between pH 6.16 and 6.26, PheB1 undergoes a significant conformational change. By pH 9.00 many residues have undergone relatively large shifts and HisB10 exhibits a double conformation. As a result of the pH increase, the occupancy of the sulfate ion decreases from a maximum of 1.00 at pH 5.00 to a minimum of 0.46 at pH 6.50. Comparison of the structures, the observed and calculated structure factors and map correlation coefficients indicate that the porcine insulin structure changes gradually as a function of pH.
Institute of Molecular Biophysics, Florida State University, Tallahassee 32306, USA. firstname.lastname@example.org