Abstract
The chapter focuses on the structure, function, and expression of epidermal growth factor (EGF) and EGF receptor. EGF is a 6.0-kilodalton (kDa) peptide comprising 53 amino-acid residues. It is formed from the 128-kDa precursor pro-EGF. There are six cysteine residues that are involved in three disulphide bridges (Cys 6-20, Cys 14-31, and Cys 33-42) to form the EGF module of three loops, A, B, and C, which are essential for stable molecular structure and for receptor binding and biological activity. EGF induces density-independent growth, reduces serum requirement for cell growth, and enhances the ability of cells to grow in soft agar, all features characteristic of cellular transformation. Genetic polymorphisms of EGF and of EGFR can conceivably affect their expression and signaling and so could be associated with susceptibility to cancer and the nature and outcome of its progression. Single nucleotide polymorphisms (SNPs) are detected in the promoter regions of the EGF gene and in the coding and non-coding regions. EGF with the 61G allele has a longer half-life than the A-allele and EGF secretion is markedly (twice) higher in hepatocellular carcinomas carrying the G/G genotypes than corresponding A/A carriers. Transforming growth factor (TGF)-α is a small mitogenic peptide with 50 amino-acid residues and three disulphide bridges. Its secondary structure closely resembles that of EGF and bears 40% sequence homology with EGF. The molecular conformation of TGF-α and EGF is determined by the disulphide bridges making provision for the formation of three loops, A, B, and C.
Published Version
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