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Lookup NU author(s): Professor Bernard Connolly
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Two exocellular nucleases with molecular masses of 18 and 34 kDa, which are nutritionally regulated and reach their maximum activity during aerial mycelium formation and sporulation, have been detected in Streptomyces antibioticus. Their function appears to be DNA degradation in the substrate mycelium, and in agreement with this proposed role the two nucleases cooperate efficiently with a periplasmic nuclease previously described in Streptomyces antibioticus to completely hydrolyze DNA. The nucleases cut DNA nonspecifically, leaving 5'-phosphate mononucleotides as the predominant products. Both proteins require Mg2+, and the additional presence of Ca2+ notably stimulates their activities. The two nucleases are inhibited by Zn2+ and aurin tricarboxylic acid. The 18-kDa nuclease from Streptomyces is reminiscent of NUC-18, a thymocyte nuclease proposed to have a key role in glucocorticoid-stimulated apoptosis. The 18-kDa nuclease was shown, by amino- terminal protein sequencing, to be a member of the cyclophilin family and also to possess peptidylprolyl cis-trans-isomerase activity. NUC-18 has also been shown to be a cyclophilin, and 'native' cyclophilins are capable of DNA degradation. The S. antibioticus 18-kDa nuclease is produced by a proteolytic processing from a less active protein precursor. The protease responsible has been identified as a serine protease that is inhibited by N(α)-p-tosyl-L- lysine chloromethyl ketone and leupeptin. Inhibition of both of the nucleases or the protease impairs aerial mycelium development in S. antibioticus. The biochemical features of cellular DNA degradation during Streptomyces development show significant analogies with the late steps of apoptosis of eukaryotic cells.
Author(s): Nicieza RG, Huergo J, Connolly BA, Sanchez J
Publication type: Article
Publication status: Published
Journal: Journal of Biological Chemistry
Year: 1999
Volume: 274
Issue: 29
Pages: 20366-20375
Print publication date: 16/07/1999
ISSN (print): 0021-9258
ISSN (electronic):
Publisher: American Society for Biochemistry and Molecular Biology, Inc.
URL: http://dx.doi.org/10.1074/jbc.274.29.20366
DOI: 10.1074/jbc.274.29.20366
PubMed id: 10400660
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