Cleavage of Amino Acid Residue(s) from the N-Terminal Region of αA- and αB-Crystallins in Human Crystalline Lens during Aging

Abstract

The current study reports for the first time a post-translational modification at the N-terminal region of αA- and αB-crystallins in normal human lens. The post-translational modification involves a loss of amino acid residues from the N-terminal region. We found three types of losses of N-terminal amino acid(s) from α-crystallin. One is the loss of the N-terminal amino acid residues 1-3 from αA-crystallin in aged lenses of the age 70 group. The other two modifications were found in αB-crystallin. One is the loss of Met(1) of the N-terminus and the other is the loss of 6 amino acids from the N-terminal region. These phenomena were observed in the lenses >40 age group. Recent studies suggest that the N-terminal region of α-crystallin may play a chaperone-like role at the molecular level. These losses of amino acids from the N-terminal region may affect this molecular chaperone-like activity as well as the transparent properties of the human lens.