The corneous layer of the claw in the lizard Anolis carolinensis mainly contains the glycine-cysteine-rich beta-protein HgGC3 in addition to hard keratins.

The localization of specific claw beta-proteins among the 40 total corneous beta-proteins present in the lizard Anolis carolinensis is not known. The hardness of claws likely depends on glycine-cysteine-rich beta-proteins content, as suggested by previous immunoblot studies. Previous studies have indicated that glycine-cysteine-rich corneous beta-proteins in addition to cysteine-rich alpha-keratins are present in the claw. In order to detect at the ultrastructural level the presence of claw-specific corneous proteins immunofluorescence and electron microscopy immunogold have been utilized. More intense immunoreactivity is obtained for the HgGC3 beta-protein while less intense immunolabeling is seen for HgGC10 and HgG5 beta-proteins and no labeling for the cysteine-rich beta-protein HgC1. The HgGC3 beta-protein appears the prevalent type present in the claw and its numerous cysteines likely form intermolecular disulphide bonds while glycine contributes hydrophobic properties to the corneous material. Other antibodies tagging the core-box and pre-core box regions of beta-proteins label with less intensity the corneous layer. The presence of cysteine-rich alpha-keratins with high homology to some human hair keratins in the dorsal part of the claw suggests that HgGC3-like beta-proteins form numerous disulphide bonds with the larger alpha-keratins giving rise to the hard corneous material of the claw.