Two different types of three-disulfide EGF domains can be differentiated on the basis of the location of the C-terminal half of disulfide c (half-cystine cC) in the structure (Bersch et al. 1998). In human EGF-like (hEGF) domains, half-cystine cC is located in the turn of the β-hairpin that comprises the minor sheet. In C1r-like (cEGF) domains, half-cystine cC is located on the minor sheet itsel f. In addition to the different position of disulfide c within the secondary str ucture, the two types of subunits differ in other respects such as the shape and orientation of the minor sheet (Bersch et al. 1998).
Superposition of the hEGF/cEGF groups using the hydrogen bonds of the minor sheet. Half-cystine cC of the hEGF group (green) is one residue out of phase in the sequence with half-cystine cC of the cEGF group (magenta). The Cα of half-cystine cC in each protein is depicted as a ball of the same colour as the backbone. The two groups of half-cystines occupy different registers with respect to the hydrogen bonds in the sheet. Four-disulfide EGF domains (cyan) adopt a hEGF-like conformation.
Back to top