Crystal structure of (L-Arg)-B0 bovine insulin at 0.21 nm resolution.

The crystal structure of (L-Arg)-B0 bovine insulin has been determined, using data to 0.21 nm and atomic parameters of 2Zn porcine insulin as a starting model, by the difference. Fourier method, the restrained least square method and X-PLOR package, interspersed with careful review of the electron density, to a final R-factor of 0.182 and r.m.s. deviation of 0.002 2 nm for the bond lengths and 4.3 degrees for the bond angles. The electron densities of additional (L-Arg)-B0 residues to B-chain N-terminus of two monomers in each asymmetric unit are very clear. The crystallographic micro-environment of the N-terminus of the B-chain is different from that of rhombohedral 2-zinc insulin.