9INS

MONOVALENT CATION BINDING IN CUBIC INSULIN CRYSTALS


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.70 Å
  • R-Value Observed: 0.178 

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This is version 1.3 of the entry. See complete history


Literature

Monovalent cation binding to cubic insulin crystals

Gursky, O.Li, Y.Badger, J.Caspar, D.L.D.

(1992) Biophys J 61: 604-611

  • DOI: 10.1016/S0006-3495(92)81865-9
  • Primary Citation of Related Structures:  
    9INS

  • PubMed Abstract: 
  • Two localized monovalent cation binding sites have been identified in cubic insulin from 2.8 A-resolution difference electron density maps comparing crystals in which the Na+ ions have been replaced by Tl+. One cation is buried in a closed cavity between insulin dimers and is stabilized by interaction with protein carbonyl dipoles in two juxtaposed alternate positions related by the crystal dyad ...

    Two localized monovalent cation binding sites have been identified in cubic insulin from 2.8 A-resolution difference electron density maps comparing crystals in which the Na+ ions have been replaced by Tl+. One cation is buried in a closed cavity between insulin dimers and is stabilized by interaction with protein carbonyl dipoles in two juxtaposed alternate positions related by the crystal dyad. The second cation binding site, which also involves ligation with carbonyl dipoles, is competitively occupied by one position of two alternate His B10 side chain conformations. The cation occupancy in both sites depends on the net charge on the protein which was varied by equilibrating crystals in the pH range 7-10. Detailed structures of the cation binding sites were inferred from the refined 2-A resolution map of the sodium-insulin crystal at pH 9. At pH 9, the localized monovalent cations account for less than one of the three to four positive counterion charges necessary to neutralize the negative charge on each protein molecule. The majority of the monovalent counterions are too mobile to show up in the electron density maps calculated using data only at resolution higher than 10 A. Monovalent cations of ionic radius less than 1.5 A are required for crystal stability. Replacing Na+ with Cs+, Mg++, Ca++ or La+++ disrupts the lattice order, but crystals at pH 9 with 0.1 M Li+, K+, NH4+, Rb+ or Tl+ diffract to at least 2.8 A resolution.


    Related Citations: 
    • Structure of the Pig Insulin Dimer in the Cubic Crystal
      Badger, J., Harris, M.R., Reynolds, C.D., Evans, A.C., Dodson, E.J., Dodson, G.G., North, A.C.T.
      (1991) Acta Crystallogr B 47: 127
    • Water Structure in Cubic Insulin Crystals
      Badger, J., Caspar, D.L.D.
      (1991) Proc Natl Acad Sci U S A 88: 622
    • Zinc-Free Cubic Pig Insulin: Crystallization and Structure Determination
      Dodson, E.J., Dodson, G.G., Lewitova, A., Sabesan, M.
      (1978) J Mol Biol 125: 387

    Organizational Affiliation

    Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, Massachusetts 02254-9110.



Macromolecules
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Entity ID: 1
MoleculeChainsSequence LengthOrganismDetailsImage
INSULIN (CHAIN A)A21Sus scrofaMutation(s): 0 
Gene Names: INS
UniProt
Find proteins for P01315 (Sus scrofa)
Explore P01315 
Go to UniProtKB:  P01315
Protein Feature View
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  • Reference Sequence
Find similar proteins by:  (by identity cutoff)  |  Structure
Entity ID: 2
MoleculeChainsSequence LengthOrganismDetailsImage
INSULIN (CHAIN B)B30Sus scrofaMutation(s): 0 
Gene Names: INS
UniProt
Find proteins for P01315 (Sus scrofa)
Explore P01315 
Go to UniProtKB:  P01315
Protein Feature View
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  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.70 Å
  • R-Value Observed: 0.178 
  • Space Group: I 21 3
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 78.9α = 90
b = 78.9β = 90
c = 78.9γ = 90
Software Package:
Software NamePurpose
PROLSQrefinement

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 1991-11-07
    Type: Initial release
  • Version 1.1: 2008-03-25
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Version format compliance
  • Version 1.3: 2017-11-29
    Changes: Derived calculations, Other