1izb
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ROLE OF B13 GLU IN INSULIN ASSEMBLY: THE HEXAMER STRUCTURE OF RECOMBINANT MUTANT (B13 GLU-> GLN) INSULIN
OverviewOverview
The assembly of the insulin hexamer brings the six B13 glutamate, side-chains at the centre into close proximity. Their mutual repulsion is, unfavourable and zinc co-ordination to B10 histidine is necessary to, stabilize the well known zinc-containing hexamers. Since B13 is always a, carboxylic acid in all known sequences of hexamer forming insulins, it is, likely to be important in the hormone's biology. The mutation of B13, Glu-->Gln leads to a stable zinc-free hexamer with somewhat reduced, potency. The structures of the zinc-free B13 Gln hexamer and the 2Zn B13, insulin hexamer have been determined by X-ray analysis and refined with, 2.5 A and 2.0 A diffraction data, respectively. Comparisons show that in, 2Zn B13 Gln insulin, the hexamer structure (T6) is very like that of the, native hormone. On the other hand, the zinc-free hexamer assumes a, quaternary structure (T3/R3) seen in the native 4Zn insulin hexamer, and, normally associated only with high chloride ion concentrations in the, medium. The crystal structures show the B13 Gln side-chains only contact, water in contrast to the B13 glutamate in 2Zn insulin. The solvation of, the B13 Gln may be associated with this residue favouring helix at B1 to, B8. The low potency of the B13 Gln insulin also suggests the residue, influences the hormone's conformation.
About this StructureAbout this Structure
1IZB is a Protein complex structure of sequences from Sus scrofa with ZN as ligand. Full crystallographic information is available from OCA.
ReferenceReference
Role of B13 Glu in insulin assembly. The hexamer structure of recombinant mutant (B13 Glu-->Gln) insulin., Bentley GA, Brange J, Derewenda Z, Dodson EJ, Dodson GG, Markussen J, Wilkinson AJ, Wollmer A, Xiao B, J Mol Biol. 1992 Dec 20;228(4):1163-76. PMID:1361949
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