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THE ROLES OF THE REL + GENE AND OF 4‐THIOURIDINE IN KILLING AND PHOTOPROTECTION OF ESCHERICHIA COLI BY NEAR‐ULTRAVIOLET RADIATION *
Author(s) -
Tsai ShungChing,
Jagger John
Publication year - 1981
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1981.tb05499.x
Subject(s) - photoprotection , escherichia coli , mutant , chemistry , biology , biophysics , photochemistry , gene , biochemistry , photosynthesis
— Photoprotection is a reduction in response to far‐UV (190–300. nm) radiation in cells that have been previously exposed to longer wavelengths. It has been proposed that photoprotection operates by means of a growth delay that permits more time for dark repair. Growth delay in Escherichia coli utilizes 4‐thiouridine ( 4 Srd) in transfer RNA as a chromophore and it requires the rel + gene, which exerts a stringent control upon RNA synthesis. Mutants that were either rel or 4 Srd − were isolated from E. coli B, utilizing a near‐UV‐induced growth‐delay selection technique. The rel mutants, which undergo little growth delay after near‐UV irradiation, show only 50% as much photoprotection as wild types, while 4 Srd − mutants show no photoprotection at all. Thus, photoprotection appears to utilize 4 Srd as its sole chromophore in E. coli B and B/r, and no more than 50% of photoprotection in these strains can be a result of near‐UV‐induced growth delay.