The subunit structure of human macrophage migration inhibitory factor: evidence for a trimer.
The subunit structure of human macrophage migration inhibitory factor (MIF) has been studied by preliminary X-ray analysis of wild-type and selenomethionine-MIF and dynamic light scattering. Crystal form I of MIF belongs to space group P2(1)2(1)2(1) and is grown from 2 M ammonium sulfate at pH 8.5. A native data set has been collected to 2.4 A resolution. Self-rotation studies and Van values indicate that three molecules per asymmetric unit are present. A data set to 2.8 A resolution has been collected for crystal form II, which belongs to space group P3(1)21 or P3(2)21 and grows from 2 M ammonium sulfate, 2% polyethylene glycol (average molecular mass 400) 0.1 M HEPES, pH 7.5. Three, four, five or six monomers in the asymmetric unit are consistent with Van values for this crystal form. Analysis of crystal form II containing selenomethionine-MIF indicates nine selenium sites are present per asymmetric unit. Dynamic light scattering of MIF suggests that the major form of the protein in solution is a trimer. The results of these studies are in contrast to previous reports indicating that MIF is a monomer or dimer. The subunit arrangement of MIF is similar to that of tumor necrosis factor and suggests that signal transduction might require trimerization of receptor subunits.
Sun
H W
HW
Department of Pharmacology, Yale University School of Medicine, New Haven, CT 06510, USA.
Swope
M
M
Cinquina
C
C
Bedarkar
S
S
Bernhagen
J
J
Bucala
R
R
Lolis
E
E
D003460:Crystallization; D018360:Crystallography, X-Ray; D006801:Humans; D008263:Macrophage Migration-Inhibitory Factors / Q000737:chemistry*; D013058:Mass Spectrometry; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry; D012542:Scattering, Radiation; D012645:Selenomethionine
D008263:Macrophage Migration-Inhibitory Factors; D011994:Recombinant Proteins; D012645:Selenomethionine