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Journal of Bacteriology, January 2008, p. 240-250, Vol. 190, No. 1
0021-9193/08/$08.00+0     doi:10.1128/JB.01528-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Processing of as-48ABC RNA in AS-48 Enterocin Production by Enterococcus faecalis{triangledown}

Matilde Fernández,1 Marina Sánchez-Hidalgo,1 Nieves García-Quintáns,2 Manuel Martínez-Bueno,1 Eva Valdivia,1 Paloma López,2 and Mercedes Maqueda1*

Departamento de Microbiología, Facultad de Ciencias, Universidad de Granada, 18071 Granada, Spain,1 Centro de Investigaciones Biológicas, CSIC, Ramiro de Maeztu 9, 28040 Madrid, Spain2

Received 21 September 2007/ Accepted 22 October 2007

Enterocin AS-48 production and immunity characters are encoded by 10 genes (as-48ABCC1DD1EFGH) of the pMB2 plasmid from the Enterococcus faecalis S-48 strain. Among these, as-48A, encoding the AS-48 peptide, and the as-48BC genes constitute a cluster required for AS-48 biogenesis and full immunity. In this study, the levels of expression of this cluster have been altered by insertion and site-directed mutagenesis as well as by expression coupled to trans complementation. Phenotypic studies of the mutants have indicated cotranscription of the three genes and revealed that the inactivation of as-48B prevents the production of AS-48, thus confirming its essentiality in AS-48 biogenesis. These studies have also supported the involvement of as-48C in enterocin immunity. In addition, they established that the intergenic region between the as-48A and as-48B genes is decisive for AS-48 expression, since a 3-bp substitution, which should disrupt a potential 47-nucleotide complex secondary structure, resulted in a hypoproducing phenotype. Transcriptional analyses of the E. faecalis wild-type and mutant strains supports the possibility that the as-48ABC genes are transcribed from the PA promoter located upstream of as-48A. Moreover, analysis and bioinformatic predictions of RNA folding indicate that as-48ABC mRNA is processed at the secondary structure located between as-48A and as-48B. Thus, synthesis of the AS-48 peptide appears to be controlled at the posttranscriptional level and is uncoupled from as-48BC translation. This mechanism of genetic regulation has not been previously described for the regulation of bacteriocin expression in enterococci.

* Corresponding author. Mailing address: Departamento Microbiología, Facultad de Ciencias, Universidad de Granada, Fuentenueva s/n, E-18071 Granada, Spain. Phone and fax: 34 958 242857. E-mail: mmaqueda{at}ugr.es

{triangledown} Published ahead of print on 2 November 2007.

Journal of Bacteriology, January 2008, p. 240-250, Vol. 190, No. 1
0021-9193/08/$08.00+0     doi:10.1128/JB.01528-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Sanchez-Hidalgo, M., Martinez-Bueno, M., Fernandez-Escamilla, A. M, Valdivia, E., Serrano, L., Maqueda, M. (2008). Effect of replacing glutamic residues upon the biological activity and stability of the circular enterocin AS-48. J Antimicrob Chemother 61: 1256-1265 [Abstract] [Full Text]  


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