VACCINIA VIRUS-19-KILODALTON PROTEIN - RELATIONSHIP TO SEVERAL MAMMALIAN PROTEINS, INCLUDING 2 GROWTH-FACTORS

Two unusual patterns of cysteine and glycine residues were observed in [rat] transforming growth factor type 1 (TGF1); a computer search found only one other protein, the 19-kilodalton early protein of vaccinia virus, having both patterns. The sequences of [mouse and human] epidermal growth factor (EGF) and of the light chains from several components of the [human and bovine] blood coagulation system also have one of the patterns, but gaps are required to adjust conserved cysteine and glycine residues in the second pattern. Several computer analyses confirmed these relationships; the 19-kilodalton protein appears to be related to TGF1 and EGF to the same degree that they are related to each other; all 3 are more distantly related to the coagulation factors. An evolutionary scheme is presented for these proteins. The conservation of cysteine residues, which form the disulfide bonds present in the active EGF molecule, may extend to conservation of disulfide bonds in these other proteins. Also, the structural similarities may be correlated with a protein-binding capability.