Dityrosine formation in calmodulin
Ultraviolet (280-nm) irradiation of bovine brain calmodulin results in calcium-dependent changes in its fluorescence emission spectrum. These consist of a decline in the intrinsic tyrosine fluorescence of the protein and the appearance of a new emission maximum at 400 nm. Chromatography of irradiated calmodulin, using Ultrogel AcA 54 and phenyl-agarose columns, yields several distinctive fractions. One of these, representing 2.8% of the total recovered protein and 53% of the total fluorescence emission at 400 nm, was selected for detailed characterization. Analyses performed on acid hydrolysates reveal the presence of dityrosine, a derivative of tyrosine known for its fluorescence near 400 nm, at the level of 0.59-0.89 mol per 16,700 g of protein. Sodium dodecyl sulfate gel electrophoresis experiments demonstrate two components of apparent molecular weights 14,000 (80%) and 16,000 (20%). Observations on the effects of UV irradiation on the thrombic fragments of calmodulin and on related calcium binding proteins (rabbit skeletal muscle troponin C, bovine cardiac troponin C, and parvalbumin) support the interpretation that dityrosine formation in calmodulin results from the intramolecular cross-linking of Tyr-99 and Tyr-138. The dityrosine-containing photoproduct of calmodulin is unable to stimulate the p-nitrophenyl phosphatase activity of calcineurin under standard assay conditions. Smooth muscle myosin light chain kinase binds the derivative about 280-fold less effectively than it binds native calmodulin. Of several metal ions tested, only Cd/sup 2 +/ approaches Ca/sup 2 +/ in its ability to promote the appearance of the 400-nm emission band during UV irradiation of calmodulin. Mn/sup 2 +/ and Cu/sup 2 +/ appear to inhibit dityrosine formation.
- Research Organization:
- Oregon State Univ., Corvallis
- OSTI ID:
- 6789545
- Journal Information:
- Biochemistry; (United States), Vol. 26:3
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CALCIUM COMPOUNDS
CONFIGURATION INTERACTION
PROTEINS
BIOLOGICAL RADIATION EFFECTS
EMISSION SPECTRA
BRAIN
CATTLE
EXTREME ULTRAVIOLET RADIATION
FLUORESCENCE
SPECTROSCOPY
TYROSINE
ALKALINE EARTH METAL COMPOUNDS
AMINO ACIDS
ANIMALS
BIOLOGICAL EFFECTS
BODY
CARBOXYLIC ACIDS
CENTRAL NERVOUS SYSTEM
DOMESTIC ANIMALS
ELECTROMAGNETIC RADIATION
HYDROXY ACIDS
LUMINESCENCE
MAMMALS
NERVOUS SYSTEM
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANS
RADIATION EFFECTS
RADIATIONS
RUMINANTS
SPECTRA
ULTRAVIOLET RADIATION
VERTEBRATES
550602* - Medicine- External Radiation in Diagnostics- (1980-)