Structural features of human leukocyte interferon A as determined by circular dichroism spectroscopy

The solution structure of human leukocyte (alpha) interferon-A (LeIF-A) purified from E. coli extracts was investigated by circular dichroism spectroscopy. At pH 8.2, the native molecule exhibits 40-70% alpha-helix and no clearly detectable beta-structure. The tertiary structure includes a closely-packed interior containing at least one tryptophan side-chain. Titration to pH 1.5 produces a partial loss of structural features which are rapidly regained on return to neutral pH.