/sup 1/H Fourier transform NMR studies of insulin: coordination of Ca/sup 2 +/ to the Glu(B13) site drives hexamer assembly and induces a conformation change

Journal Article · Tue May 03 00:00:00 EDT 1988 · Biochemistry; (United States)

OSTI ID:7142948

Palmieri, R; Lee, R W.K.; Dunn, M F

/sup 1/H Fourier transform NMR investigations of metal ion binding to insulin in /sup 2/H/sub 2/O were undertaken as a function of pH to determine the effects of metal ion coordination to the Glu(B13) site on the assembly and structure of the insulin hexamer. The C-2 histidyl regions of the /sup 1/H NMR spectra of insulin species containing respectively one Ca/sup 2 +/ and two Zn/sup 2 +//hexamer and three Cd/sup 2 +//hexamer have been assigned. Both the Cd/sup 2 +/ derivative (In)/sub 6/(Cd/sup 2 +/)/sub 2/Cd/sup 2 +/, where two of the Cd/sup 2 +/ ions are coordinated to the His(B10) sites and the remaining Cd/sup 2 +/ ion is coordinated to the Glu(B13) site and the Zn/sup 2 +/-Ca/sup 2 +/ derivative (In)/sub 6/..sqrt.. (Zn/sup 2 +/)/sub 2/Ca/sup 2 +/, where the two Zn/sup 2 +/ ions are coordinated to the His(B10) sites and Ca/sup 2 +/ ion is coordinated to the Glu(B13) site, give spectra in which the C-2 proton resonances of His(B10) are shifted upfield relative to metal-free insulin. Spectra of insulin solutions containing a ratio of In:Zn/sup 2 +/ = 6:2 in the pH* region from 8.6 to 10 were found to contain signals both from metal-free insulin species and from the 2ZN-insulin hexamer, (In)/sub 6/(Zn/sup 2 +/)/sub 2/. The authors postulate that the additional thermodynamic drive provided by Ca/sup 2 +/ and Cd/sup 2 +/ is due to coordination of these metal ions to the Glu(B13) carboxylates of the hexamer. Comparison of the aromatic regions of the /sup 1/H NMR spectra for (In)/sub 6/(Zn/sup 2 +/)/sub 2/ with (In)/sub 6/(n/sup 2 +/)/sub 2/Ca/sup 2 +/, (In)/sub 6/(Cd/sup 2 +/)/sub 2/Cd/sup 2 +/, and (In)/sub 6/(Cd/sup 2 +/)/sub 2/Ca/sup 2 +/ indicates that binding of either Ca/sup 2 +/ or Cd/sup 2 +/ to the Glu(B13) site induces a conformation change that perturbs the environments of the side chains of several of the aromatic residues in the insulin structure. Since these residues lie on the monomer-monomer and dimer-dimer subunit interfaces, conformation change includes small changes in the subunit interfaces that alter the microenvironments of the aromatic rings.

• Research Organization: Univ. of California, Riverside (USA)
• OSTI ID: 7142948
• Journal Information: Biochemistry; (United States), Vol. 27:9
• Country of Publication: United States
• Language: English

Related Subjects

62 RADIOLOGY AND NUCLEAR MEDICINE
CATIONS
CONFIGURATION INTERACTION
INSULIN
CONFORMATIONAL CHANGES
NUCLEAR MAGNETIC RESONANCE
CALCIUM COMPOUNDS
FOURIER TRANSFORMATION
HEAVY WATER
PH VALUE
PROTONS
ALKALINE EARTH METAL COMPOUNDS
BARYONS
CHARGED PARTICLES
ELEMENTARY PARTICLES
FERMIONS
HADRONS
HORMONES
HYDROGEN COMPOUNDS
INTEGRAL TRANSFORMATIONS
IONS
MAGNETIC RESONANCE
NUCLEONS
OXYGEN COMPOUNDS
PEPTIDE HORMONES
RESONANCE
TRANSFORMATIONS
WATER
550601* - Medicine- Unsealed Radionuclides in Diagnostics