Determination of the monomer-dimer equilibrium of interleukin-8 reveals it is a monomer at physiological concentrations.
Interleukin-8 has been shown by X-ray crystallography and NMR to be a homodimer, suggesting that this is the form which binds to its receptor. Here we measure, for the first time, the monomer-dimer equilibrium of interleukin-8 using analytical ultracentrifugation and titration microcalorimetry and find that it dissociates readily to monomers with an equilibrium dissociation constant of 18 +/- 6 microM at 37 degrees C. The present findings suggest that the monomer is the form which binds to the receptor. Comparison of experimental and structure-based calculated thermodynamics of interleukin-8 dimerization argues for limited subunit conformational changes upon dissociation to monomer.
Burrows
S D
SD
Department of Macromolecular Sciences, SmithKline Beecham Pharmaceuticals, King of Prussia, Pennsylvania 19406.
Doyle
M L
ML
Murphy
K P
KP
Franklin
S G
SG
White
J R
JR
Brooks
I
I
McNulty
D E
DE
Scott
M O
MO
Knutson
J R
JR
Porter
D
D
D002151:Calorimetry; D004926:Escherichia coli; D005454:Fluorescence Polarization; D006801:Humans; D016209:Interleukin-8 / Q000737:chemistry*; D046911:Macromolecular Substances; D009682:Magnetic Resonance Spectroscopy; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry; D013816:Thermodynamics; D014461:Ultracentrifugation
D016209:Interleukin-8; D046911:Macromolecular Substances; D011994:Recombinant Proteins