Shigenobu Kimura

Stability of human interferon-ß1: oligomeric human interferon-ß1 is inactive but is reactivated by monomerization

Human interferon-s1 is extremely stable in a low ionic strength solution of pH 2 such as 10 mM HCl at 37°C. However, the presence of 0.15 M NaCl led to a remarkable loss of antiviral activity. The molecular-sieve high-performance liquid chromatography revealed that, whereas completely active human interferon-s1 eluted as a 25 kDa species (monomeric form), the inactivated preparation eluted primarily as a 90 kDa species (oligomeric form). The specific activity (units per protein) of the oligomeric form was approx. 10% of that of the monomeric form. This observation shows that oligomeric human interferon-s1 is apparently in an inactive form. When the oligomeric eluate was resolved by polyacrylamide gel containing sodium dodecyl sulphate (SDS), it appeared to be monomeric under non-reducing conditions. Monomerization of the oligomeric human interferon-s1 by treatment with 1% SDS, fully regenerated its antiviral activity. These results suggest that the inactivation of the human interferon-s1 preparation was caused by its oligomerization via hydrophobic interactions without the formation of intermolecular disulphide bonds. These oligomers can be dissociated by SDS to restore biological activity.

Sequence of a cDNA coding for bovine pancreatic phospholipase A2

Phospholipaae A2 (PLA2) from pancreas has the following interesting features. The enzyme preferably acts on aggregated phospholipid micell-like structures, requires Ca + + for its activity, and is produced as a zymogen (1). To elucidate the relationship between these features and the structure of this enzyme, the gene encoding it and the expression system will be a useful tool. We have isolated a cDNA coding for bovine pancreatic PLA2 from a pancreatic cDNA library. The cDNA encodes a 130 amino acids proPLA2 with a 15 amino acido signal polypeptide. The deduced proPLA2 amino acid sequence is consistent with the previously reported one except for the 122th Asn replaced with Lys, and the first residue pyroglutamic acid is encoded as Gln(--7th) by the cDNA (2,3). The sequence of the signal polypeptide is similar to that of other PLA2 (4,5).