Ultraviolet-induced photodegradation of cucumber (Cucumis sativus L. ) microsomal and soluble protein tryptophanyl residues in vitro

Journal Article · Mon Mar 01 00:00:00 EST 1993 · Plant Physiology; (United States)

OSTI ID:6384009

Caldwell, C R ^[1]

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1. Dept. of Agriculture, Beltsville, MD (United States)

The in vitro effects of ultraviolet B (280--320 nm) radiation on microsomal membrane proteins and partially purified ribulose bisphosphate carboxylase (Rubisco) from cucumber (Cucumis sativus L.) was investigated by measuring the direct photolytic reduction of tryptophan fluorescence and the formation of fluorescent photooxidation products. Exposure of microsomes and Rubisco to monochromatic 300-nm radiation resulted in the loss of intrinsic tryptophan fluorescence and the production of blue-emitting fluorophores. The major product of tryptophan photolysis was tentatively identified as N-formylkynurenine (N-FK). Even though the rates of tryptophan photodegradation and N-FK formation were similar, the amount of blue fluorescence produced was significantly higher in the microsomes relative to Rubisco. Studies with various free radical scavengers and other modifiers indicated that tryptophan photodegradation requires oxygen species. The optimum wavelengths for loss of tryptophan fluorescence were 290 nm for the microsomes and 280 nm for Rubisco. The temperature dependence of tryptophan fluorescence and rate of tryptophan photodegradation indicated an alteration in the cucumber microsomal membranes at about 24[degrees]C, which influenced protein structure and tryptophan photosensitivity. 29 refs., 6 figs., 1 tab.

• OSTI ID: 6384009
• Journal Information: Plant Physiology; (United States), Vol. 101:3; ISSN 0032-0889
• Country of Publication: United States
• Language: English

Related Subjects

63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
CUCUMBERS
PHOTOLYSIS
TRYPTOPHAN
ULTRAVIOLET RADIATION
BIOLOGICAL EFFECTS
CARBOXYLASE
FLUORESCENCE
IN VITRO
MEMBRANE PROTEINS
MICROSOMES
PHOTOSENSITIVITY
PROTEIN STRUCTURE
WAVELENGTHS
AMINO ACIDS
AROMATICS
AZAARENES
AZOLES
CARBON-CARBON LYASES
CARBOXY-LYASES
CARBOXYLIC ACIDS
CELL CONSTITUENTS
CHEMICAL REACTIONS
DECOMPOSITION
ELECTROMAGNETIC RADIATION
ENZYMES
FOOD
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
INDOLES
LUMINESCENCE
LYASES
MAGNOLIOPHYTA
MAGNOLIOPSIDA
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
PLANTS
PROTEINS
PYRROLES
RADIATIONS
RIBOSOMES
SENSITIVITY
VEGETABLES
560120* - Radiation Effects on Biochemicals
Cells
& Tissue Culture
560140 - Radiation Effects on Plants