Isolation and some properties of arachin subunits.

Abstract

Six kinds of arachin subunits were isolated by isoelectric focusing in sucrose density gradient in the presence of 6M urea and 0.2M, I-mercaptoethanol. These subunits (S1 to S6) had different isoelectric points (pI 5.8, 6.0, 6.3, 7.1, 7.4 and 8.3) and they were found in parent arachin in the weight ratio of 2.5:2.2:2.6:1.6:1.1:1.0. The molecular weights and N-terminal amino acids of the isolated subunits were 35, 500 and valine (S1), 37, 500 and isol-eucine (S2), 40, 500 and isoleucine (S3) and 19, 500 and glycine (S4, S5 and S6). While, the parent arachin contained approximately one mole of valine, two moles of isoleucine and three moles of glycine as the N-terminal amino acids per 180, 000g. It is, therefore, concluded that arachin consists of six different subunits to form the molecular weight 180, 000. No disulfide bond takes part in the subunit association of arachin, because the dissociation in a urea solu-tion occurred in the absence of β-mercaptoethanol.