An additional locus (PI4) in the protease inhibitor (PI) gene cluster of pigs

Summary A further α-protease inhibitor system, PI4, was detected in porcine sera using either 2D agarose gel, pH 5.0-PAGE, pH 9.0, or ID PAGE followed by immunoblotting with rabbit anti-porcine PI2 or PI3 antisera. PI4 inhibited chymotrypsin, but not trypsin. Seven allelic variants of PI4 were described. By haplotyping of a-protease inhibitor systems in 52 complete families it was shown that PI4 locus belongs to the PI gene cluster. The probable order of the PI loci was: PI1, PO1A, PI2, PI4, PI3.