NMR studies of the solution properties of recombinant murine interleukin-6.
The effects of solvent, pH and temperature on the 1H-NMR spectra of recombinant murine interleukin-6 (IL-6) are described. Assignments made from two-dimensional homonuclear spectra are presented for resonances of the fifteen aromatic amino-acid side chains. A time-dependent loss of intensity was observed for all resonances in the spectrum of IL-6, probably as a result of aggregation. This aggregation is markedly temperature-dependent. The pKa values of the four histidine residues in murine IL-6 has been measured; one has a value of 5.5, approx. one pH unit less than the value exhibited by the other three. Analysis of the NOESY spectra has allowed a preliminary characterisation of the nature of interactions among the aromatic side chains within the protein fold. 1H and 15N resonances of residues Thr-4 to Val-21 are assigned from three-dimensional 1H-15N correlated spectroscopy, and evidence is presented for these residues comprising a mobile N-terminal tail with little ordered structure. An N-terminal mutant lacking the first 22 residues of the murine IL-6 sequence and known to possess full biological activity was also examined and shown to have essentially retained the tertiary fold of the native molecule.
Morton
C J
CJ
Joint Protein Structure Laboratory, Ludwig Institute for Cancer Research, Parkville, Vic., Australia.
Bai
H
H
Zhang
J G
JG
Hammacher
A
A
Norton
R S
RS
Simpson
R J
RJ
Mabbutt
B C
BC
D000595:Amino Acid Sequence; D000818:Animals; D006863:Hydrogen-Ion Concentration; D015850:Interleukin-6 / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D051379:Mice; D008969:Molecular Sequence Data; D011994:Recombinant Proteins / Q000737:chemistry; D016415:Sequence Alignment; D012996:Solutions; D012997:Solvents; D013696:Temperature
D015850:Interleukin-6; D011994:Recombinant Proteins; D012996:Solutions; D012997:Solvents