Effects of carotenoids from Deinococcus radiodurans on protein oxidation

Aims:  To evaluate the antioxidant effect of carotenoids from Deinococcus radiodurans on protein.
Methods and Results:  Deinococcus radiodurans strain R1 (ATCC 13939) and its mutant strain R1ΔcrtB were used for this study. The total carotenoids (R1ex) from D. radiodurans were obtained by extraction with acetone/methanol (7 : 2, by vol), and their antioxidant activity was measured using the DPPH˙ (2,2-diphenyl-1-picrylhydrazyl) system. The protein oxidation level, in vitro and in the cell, was measured using the DNPH (2,4-dinitrophenyl hydrazine) method. The carotenoid extract R1ex scavenged 40·2% DPPH˙ radicals compared to β-carotene (31·7%) at a concentration of 0·5 mg ml⁻¹. The intracellular level of protein oxidation in mutant R1ΔcrtB, which does not contain carotenoid, was 0·0212 mmol mg⁻¹ protein which is significantly greater than that in the wild type (0·0169 mmol mg⁻¹ protein) following the treatment with H₂O₂. The purified major carotenoid product (deinoxanthin) from the wild type showed a greater inhibition of oxidative damage in bovine serum albumin than lycopene or lutein.
Conclusions:  Carotenoids prevent protein oxidation and contribute to the resistance to cell damage in D. radiodurans .
Significance and Impact of the Study:  Our results provide the evidence that carotenoids can protect proteins in D. radiodurans against oxidative stress.