Chicken liver TGGCA protein purified by preparative mobility shift electrophoresis (PMSE) shows a 36.8 to 29.8 kd microheterogeneity.

The TGGCA protein, the chicken homologue of HeLa cell NF-I, was purified to homogeneity from liver tissue by a procedure which includes preparative mobility shift electrophoresis (PMSE) as the final step. PMSE was here adjusted for the isolation of the TGGCA protein, but can be used as a general method to characterize the protein moiety of specific DNA-binding proteins. The TGGCA protein is a family of 6 protein species, which show minor differences in molecular weight from 36.8kd to 29.8kd. This microheterogeneity differs from the size distribution reported for HeLa cell NF-I polypeptides. All species of the TGGCA protein bind identically to a synthetic DNA-binding site and appear to be highly related in primary structure. We discuss the possible functional importance of this microheterogeneity.