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GK Klintworth, C Hedegaard, Z Valnickova, IB Thogersen, JJ Enghild; Purification and Characterization of Transforming Growth Factor Beta Induced Protein from Porcine Cornea . Invest. Ophthalmol. Vis. Sci. 2002;43(13):1737.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To purify and characterize the primary structure of transforming growth factor induced protein from a natural source in a mammalian species with a large cornea. Such studies were performed because this poorly understood protein is a significant constituent of the normal cornea and different mutations in the TGFB1 (BIGH3) gene cause a variety of inherited human corneal diseases that are characterized by extracellular accumulations of the mutant protein. Methods: TGFB1 encoded protein was extracted from fresh porcine corneas and purified by a combination of hydrophobic interaction chromatography, ion exchange chromatography and gel filtration. The purified protein was cleaved and the peptides were analyzed by HPLC, Edman degradation mass spectrometry and by FACE carbohydrate analysis. Results: The amino acid sequence of the porcine transforming growth factor protein isolated in these studies was more than 80% identical to the equivalent human protein. A chemical analysis of the protein showed that it is a glycoprotein, composed of one or two subunits. In addition the COOH-terminal of the mature form including the RGD sequence was truncated. Conclusion: The results suggest that transforming growth factor beta induced protein exists as both a glycosylated monomer and as a non-covalently associated glycosylated homo-dimer. The majority of the mature form is truncated lacking the COOH-terminal domain containing the RGD sequence. Further studies on the purified protein in porcine and human corneas should provide further insight into the nature of the corneal deposits in those corneal dystrophies caused by mutations in the TGFB1 gene.
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