Complementary deoxyribonucleic acid cloning of bovine transforming growth factor-beta 1

Transforming growth factor-beta 1 (TGF beta 1) has been purified from a number of different sources and has a broad species specificity. To deduce the complete amino acid sequence of bovine TGF beta 1 we have isolated cDNA clones encoding the protein from a bovine fibropapilloma library using a human cDNA probe. Sequence analysis of two independent cDNA clones revealed that the 112 amino acids corresponding to bovine TGF beta 1 are identical to those of the human and porcine proteins. This unusually high degree of conservation in the primary structure of the human and bovine proteins reflects the strong evolutionary constraints for maintenance of structure and function of the molecule. As in the human, murine, and porcine systems, the mature form of TGF beta 1 is derived by proteolytic cleavage of a larger precursor. Small differences in amino acid sequence were observed in the portion of the precursor that does not include mature TGF beta 1, although 92% of the residues are still conserved. A 2.25 kilobase (kb) mRNA was identified in total bovine wart and bone RNA, whereas no message was detected in polyadenylated spleen or brain RNA. In addition to the major 2.25 kb message, we observed a 1.9 kb transcript in poly(A+) RNA from wart tissue.