Identification of the metastasis-associated, galactoside-binding lectin as a chimeric gene product with homology to an IgE-binding protein.

We report the complete primary and secondary structures of a metastasis-associated Mr 34,000 galactoside-binding lectin. The polypeptide sequence (264 amino acids) was derived from the nucleotide sequence of three overlapping complementary DNA clones isolated from lambda gt11 and lambda gt10 phage libraries of UV-induced murine fibrosarcomas. Striking features of the polypeptide sequence are two distinct regions of beta-sheet and globular structures at the amino and carboxy terminals, respectively. Homology search suggests that the polypeptide is a chimeric gene product formed by fusion of the 5'-end of an Mr approximately 14,000 galactoside-binding lectin with an internal domain of the collagen alpha gene. Enzymatic treatment with collagenase confirmed the presence of a collagen-like structure in the polypeptide. Unexpectedly, the entire sequence is greater than 85% homologous to a rat low affinity IgE-binding protein.