PMID- 10521251
OWN - NLM
STAT- MEDLINE
DCOM- 19991117
LR  - 20190613
IS  - 0006-2960 (Print)
IS  - 0006-2960 (Linking)
VI  - 38
IP  - 41
DP  - 1999 Oct 12
TI  - Role of metal ions in the T- to R-allosteric transition in the insulin hexamer.
PG  - 13443-52
AB  - The role of metal ions in the T- to R-allosteric transition is ascertained from
      the investigation of the T- to R-allosteric transition of transition metal ions
      substituted-insulin hexamers, as well as from the kinetics of their dissociation.
      These studies establish that ligand field stabilization energy (LFSE),
      coordination geometry preference, and the Lewis acidity of the metal ion in the
      zinc sites modulate the T- to R-state transition. (1)H NMR, (113)Cd NMR, and
      UV-vis measurements demonstrate that, under suitable conditions, Fe2+/3+, Ni2+,
      and Cd2+ bind insulin to form stable hexamers, which are allosteric species. (1)H
      NMR R-state signatures are elicited by addition of phenol alone in the case of
      Ni(II)- and Cd(II)-substituted insulin hexamers. The Fe(II)-substituted insulin
      hexamer is converted to the ferric analogue upon addition of phenol. For the
      Fe(III)-substituted insulin hexamer, appearance of (1)H NMR R-state signatures
      requires, additionally to phenol, ligands containing a nitrogen that can donate a
      lone pair of electrons. This is consistent with stabilization of the R-state by
      heterotropic interactions between the phenol-binding pocket and ligand binding to
      Fe(III) in the zinc site. UV-vis measurements indicate that the (1)H NMR detected
      changes in the conformation of the Fe(III)-insulin hexamer are accompanied by a
      change in the electronic structure of the iron site. Kinetic measurements of the 
      dissociation of the hexamers provide evidence for the modulation of the stability
      of the hexamer by ligand field stabilization effects. These kinetic studies also 
      demonstrate that the T- to R-state transition in the insulin hexamer is governed 
      by coordination geometry preference of the metal ion in the zinc site and the
      compatibility between Lewis acidity of the metal ion in the zinc site and the
      Lewis basicity of the exogenous ligands. Evidence for the alteration of the
      calcium site has been obtained from (113)Cd NMR measurements. This finding adds
      to the number of known conformational changes that occur during the T- to
      R-transition and is an important consideration in the formulation of allosteric
      mechanisms of the insulin hexamer.
FAU - Kadima, W
AU  - Kadima W
AD  - Department of Chemistry, State University of New York at Oswego 13126, USA.
      kadima@oswego.edu
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
PL  - United States
TA  - Biochemistry
JT  - Biochemistry
JID - 0370623
RN  - 0 (Ferric Compounds)
RN  - 0 (Ferrous Compounds)
RN  - 0 (Insulin)
RN  - 0 (Isotopes)
RN  - 0 (Metals, Heavy)
RN  - 0 (Protons)
RN  - 00BH33GNGH (Cadmium)
RN  - 7OV03QG267 (Nickel)
RN  - SY7Q814VUP (Calcium)
SB  - IM
MH  - Allosteric Regulation
MH  - Allosteric Site
MH  - Cadmium/chemistry
MH  - Calcium/chemistry
MH  - Ferric Compounds/chemistry
MH  - Ferrous Compounds/chemistry
MH  - Humans
MH  - Insulin/*chemistry
MH  - Isotopes
MH  - Kinetics
MH  - Metals, Heavy/*chemistry
MH  - Nickel/chemistry
MH  - Nuclear Magnetic Resonance, Biomolecular
MH  - Protein Conformation
MH  - Protons
MH  - Spectrophotometry, Ultraviolet
EDAT- 1999/10/16 00:00
MHDA- 1999/10/16 00:01
CRDT- 1999/10/16 00:00
PHST- 1999/10/16 00:00 [pubmed]
PHST- 1999/10/16 00:01 [medline]
PHST- 1999/10/16 00:00 [entrez]
AID - bi9903188 [pii]
AID - 10.1021/bi9903188 [doi]
PST - ppublish
SO  - Biochemistry. 1999 Oct 12;38(41):13443-52. doi: 10.1021/bi9903188.