title: Molecular changes during the photooxidation of alpha-crystallin in the presence of uroporphyrin.
abstract: Singlet oxygen reacts preferentially with three amino acids in proteins, His, Trp and Met. In order to study the specific molecular events that result from such oxidations, calf alpha-crystallin was photooxidized in the presence of uroporphyrin and the reactions were investigated by high performance liquid chromatography peptide mapping using a photodiode array detector followed by fast atom bombardment mass spectrometry (FAB-MS). From these studies, the following conclusions can be inferred: (1) Upon photooxidation residue Met-68 of the B chain is oxidized to Met sulfoxide, whereas residue Trp-60 remains intact. (2) Two of the 16 His residues in alpha-crystallin are photooxidized with an apparent pKa of ca 7.0 (3) FAB-MS analysis suggests that residue Lys-166 close to the C-terminal end of the A chain forms a cross-link with the His-7 residue close to the N-terminal end of the A chain. This may be either an inter- or intramolecular cross-link.
authors: Department of Ophthalmology, Columbia University, New York, NY 10032.
authors: J
authors: J
authors: Dillon
authors: R
authors: R
authors: Chiesa
authors: R H
authors: RH
authors: Wang
authors: M
authors: M
authors: McDermott
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D003459:Crystallins / Q000737:chemistry / Q000302:isolation & purification / Q000528:radiation effects*; D006863:Hydrogen-Ion Concentration; D007908:Lens, Crystalline; D008027:Light; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000302:isolation & purification; D016339:Spectrometry, Mass, Fast Atom Bombardment; D014578:Uroporphyrins / Q000494:pharmacology*
chemical_list: D003459:Crystallins; D010446:Peptide Fragments; D014578:Uroporphyrins