Sequence characterization of alleles Gpi1-Sa and Gpi1-Sb at the glucose phosphate isomerase structural locus

The sequences of alleles Gpi1-sa and Gpi1-sb at the glucose phosphate isomerase structural locus have been determined from cDNA of the mouse inbred strains 101/H Gpi1-sa and C3H/HeH Gpi1-sb by RT PCR and direct sequencing of the amplified products. Four individual nucleotide differences were observed between the two alleles. The difference at amino acid residue 94, (Gpi1-sa GAT Asp, Gpi1-sb AAT Asn) may account for the differing electrophoretic migration, isoelectric point, and thermostability of the two alleles. Two of the other observed differences in the coding region (amino acid residue 12 Leu, Gpi1-sa CTC, Gpi1-sb CTG and amino acid residue 17 Arg, Gpi1-sa CGC, Gpi1-sb CGT) are silent and do not affect the predicted amino acid residues on translation. The fourth observed difference is located within the 3' noncoding sequences of the cDNA. The change at amino acid residue 94 is associated with the presence of a Hinf1 restriction site in Gpi1-sb, which is absent in Gpi1-sa, and may be a useful method for determining this marker.