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Journal of Bacteriology, October 2008, p. 6448-6457, Vol. 190, No. 19
0021-9193/08/$08.00+0 doi:10.1128/JB.00557-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Tungalag Chuluunbaatar,1
Katalin F. Medzihradszky,2,4 and
Lajos Alföldi3
Institute of Biochemistry,1 Proteomics Research Group,2 Institute of Genetics, Biological Research Center of the Hungarian Academy of Sciences, Szeged, Hungary,3 Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, California 94143-22404
Received 22 April 2008/ Accepted 28 July 2008
Upon induction, Bacillus megaterium 216 produces the bacteriocin megacin A-216, which leads to lysis of the producer cell and kills B. megaterium and a few other bacterial species. The DNA region responsible for megacinogeny was cloned in B. megaterium. The nucleotide sequence of a 5,494-bp-long subfragment was determined, and the function of the genes on this fragment was studied by generating deletions and analyzing their effects on MegA phenotypes. An open reading frame (ORF) encoding a 293-amino-acid protein was identified as the gene (megA) coding for megacin A-216. BLAST searches detected sequence similarity between megacin A-216 and proteins with phospholipase A2 activity. Purified biologically active megacin A-216 preparations contained three proteins. Mass spectrometry analysis showed that the largest protein is the full-length translation product of the megA gene, whereas the two shorter proteins are fragments of the long protein created by cleavage between Gln-185 and Val-186. The molecular masses of the three polypeptides are 32,855, 21,018, and 11,855 Da, respectively. Comparison of different megacin preparations suggests that the intact chain as well as the two combined fragments can form biologically active megacin. An ORF located next to the megA gene and encoding a 91-amino-acid protein was shown to be responsible for the relative immunity displayed by the producer strain against megacin A-216. Besides the megA gene, at least two other genes, including a gene encoding a 188-amino-acid protein sharing high sequence similarity with RNA polymerase sigma factors, were shown to be required for induction of megacin A-216 expression.
Published ahead of print on 8 August 2008.
Present address: Institute of Medical Chemistry, Szeged University, 6720 Szeged, Dóm tér 8., Hungary.
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