Specific racemization and isomerization of the aspartyl residue of alphaA-crystallin due to UV-B irradiation.
We have reported that the aspartyl (Asp)-151 residue in alphaA-crystallin in human eye lens was inverted to the D-isomer and isomerized to beta-Asp residue with age. We report here that ultraviolet (UV)-B irradiation induces the racemization and isomerization of the Asp-151 residue of alphaA-crystallin from lenses of 6-week-old rats to form D-isomer and beta-Asp residue. Simultaneous racemization and isomerization of the specific Asp residue indicate that the reaction proceeds via formation of a succinimide intermediate. This modification was not observed in UV-A irradiated and normal lenses. UV-B irradiation induced the racemization of only the Asp-151 residue and did not affect the other Asp residues in alphaA-crystallin. On the other hand, the high molecular weight fraction of the lens protein increased upon UV-B irradiation. Modification of the Asp residue would affect the three-dimensional packing array of the lens protein.
Fujii
N
N
Field and Reaction, Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Corporation (JST), Nervous Informatics Laboratory, National Institute of Bioscience and Human-technology, Tsukuba, Ibaraki, 305, Japan.
Momose
Y
Y
Ishibashi
Y
Y
Uemura
T
T
Takita
M
M
Takehana
M
M
D000595:Amino Acid Sequence; D000818:Animals; D001216:Asparagine / Q000737:chemistry / Q000528:radiation effects; D001224:Aspartic Acid / Q000737:chemistry / Q000528:radiation effects*; D003459:Crystallins / Q000737:chemistry / Q000528:radiation effects*; D007536:Isomerism; D008969:Molecular Sequence Data; D051381:Rats; D017208:Rats, Wistar; D014466:Ultraviolet Rays
D003459:Crystallins; D001224:Aspartic Acid; D001216:Asparagine