1APH

CONFORMATIONAL CHANGES IN CUBIC INSULIN CRYSTALS IN THE PH RANGE 7-11

Summary for 1APH

• Entry DOI: 10.2210/pdb1aph/pdb
• Related: 1BPH 1CPH 1DPH
• Descriptor: INSULIN A CHAIN (PH 7), INSULIN B CHAIN (PH 7), 1,2-DICHLOROETHANE, ... (4 entities in total)
• Functional Keywords: hormone
• Biological source: Bos taurus (cattle); More
• Cellular location: Secreted: P01317 P01317
• Total number of polymer chains: 2
• Total formula weight: 5842.53

Authors

Gursky, O.,Badger, J.,Li, Y.,Caspar, D.L.D. (deposition date: 1992-10-30, release date: 1993-01-15, Last modification date: 2024-10-16)

Primary citation

Gursky, O.,Badger, J.,Li, Y.,Caspar, D.L.
Conformational changes in cubic insulin crystals in the pH range 7-11.
Biophys.J., 63:1210-1220, 1992

PubMed Abstract: To determine the effect of variations in the charge distribution on the conformation of a protein molecule, we have solved the structures of bovine cubic insulin over a pH range from 7 to 11 in 0.1 M and 1 M sodium salt solutions. The x-ray data were collected beyond 2-A resolution and the R factors for the refined models ranged from 0.16 to 0.20. Whereas the positions of most protein and well-ordered solvent atoms are conserved, about 30% of residues alter their predominant conformation as the pH is changed. Conformational switching of A5 Gln and B10 His correlates with the pH dependence of monovalent cation binding to insulin in cubic crystals. Shifts in the relative positions of the A chain NH2-terminal and B chain COOH-terminal groups are probably due to titration of the A1 alpha-amino group. Two alternative positions of B25 Phe and A21 Asn observed in cubic insulin at pH 11 are similar to those found in two independent molecules of the 2Zn insulin dimer at pH 6.4. The conformational changes of the insulin amino acids appear to be only loosely coupled at distant protein sites. Shifts in the equilibrium between distinct conformational substates as the charge distribution on the protein is altered are analogous to the electrostatically triggered movements that occur in many functional protein reactions.

PubMed: 1477273

Experimental method

X-RAY DIFFRACTION (2 Å)