3ins
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STRUCTURE OF INSULIN. RESULTS OF JOINT NEUTRON AND X-RAY REFINEMENT
OverviewOverview
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.
About this StructureAbout this Structure
3INS is a Protein complex structure of sequences from Sus scrofa with ZN and DOD as ligands. Full crystallographic information is available from OCA.
ReferenceReference
Structure of insulin: results of joint neutron and X-ray refinement., Wlodawer A, Savage H, Dodson G, Acta Crystallogr B. 1989 Feb 1;45 ( Pt 1):99-107. PMID:2695122
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