Thrombospondin 4 (THBS4)

Thrombospondin 4 (THBS4) was originally identified from a Xenopus stage 45 cDNA library.Overall, the 961-amino acid predicted protein is 73% identical to the X. laevis sequence; however, the C-terminal 220 residues are over 92% identical. The TSP4 mRNA is approximately 3.4 kb. In contrast to thrombospondin-4 of Xenopus laevis, the human protein contains an RGD (arg-gly-asp) cell-binding sequence in the third type 3 repeat.

Transfection of mouse NIH 3T3 fibroblasts or C2C12 myoblasts with a full-length human thrombospondin-4 cDNA resulted in the expression of a polypeptide with a reduced molecular weight of 140,000. In the absence of reducing agent, the expressed protein had an apparent molecular weight of 550,000.