PDBsum entry 3ins

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Hormone PDB id
Protein chains
21 a.a. *
30 a.a. *
DOD ×321
_ZN ×2
* Residue conservation analysis

References listed in PDB file
Key reference
Title Structure of insulin: results of joint neutron and X-Ray refinement.
Authors A.Wlodawer, H.Savage, G.Dodson.
Ref. Acta Crystallogr B, 1989, 45, 99.
PubMed id 2695122
Neutron diffraction data for porcine 2Zn insulin were collected to 2.2 A resolution from a single crystal deuterated by slow exchange of mother liquor. A joint neutron/X-ray restrained-least-squares refinement was undertaken using the neutron data, as well as the 1.5 A resolution X-ray data collected previously. The final R factors were 0.182 for the X-ray data and 0.191 for the neutron data. Resulting atomic coordinates were compared with the initial X-ray model, showing a total r.m.s. shift of 0.36 A for the protein and 0.6 A for the solvent. Protonation of a number of individual amino acids was investigated by analysis of the neutron maps. No D atoms were found between the carboxylates of Glu B13 which make an intermolecular contact, suggesting nonbonded interaction rather than the predicted hydrogen bond. Amide hydrogen exchange was investigated in a refinement of their atomic occupancies. Regions of unexchanged amide groups were found in the center of the B helices. The results of this study emphasize the limited amount of information available in neutron diffraction studies of proteins at resolution lower than 2 A.
Secondary reference #1
Title Experience with fast fourier least squares in the refinement of the crystal structure of rhombohedral 2-Zinc insulin at 1.5 angstroms resolution
Authors N.W.Isaacs, R.C.Agarwal.
Ref. acta crystallogr.,sect.a, 1978, 34, 782.
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