MOLECULAR EVIDENCE FOR HUMAN ALPHA2-HS GLYCOPROTEIN (AHSG) POLYMORPHISM

Alpha2-HS glycoprotein (AHSG) is a human plasma glycoprotein that exhi bits genetic polymorphism on isoelectric focusing (IEF). To identify t he origin of two common alleles, AHSG1 and *2, we examined nucleotide exchanges in the gene. AHSG cDNA was obtained by RT-PCR from poly(A) RNA of seven liver tissue samples and subcloned into a plasmid vector. After sequencing, we found six single nucleotide differences in compa rison with the originally reported sequence. In particular, the nucleo tide substitutions of C to T at amino acid position 230 and C to G at position 238 were common among the samples exhibiting phenotype 2-1 or 2. Since these substitutions might give rise to a NlaIII site and a S acI site, respectively for the potential AHSG2, we analyzed these sub stitutions by PCR-RFLP using genomic DNA of 68 individuals. The result was consistent with the IEF analysis of the corresponding serum, indi cating that AHSG1 was characterized by ACG (Thr) at position 230 in e xon 6 and ACC (Thr) at position 238 in exon 7, and that AHSG2 was cha racterized by ATG (Met) at position 230 and AGC (Ser) at position 238.