f Sequencing and analysis of the Bacillus subtilis lytRABC divergon: A regulatory unit encompassing the structural genes of the N-acetylmuramoyl-L-alanine amidase and its modifier
- Authors: Vladimir Lazarevic, Philippe Margot, Blazenka Soldo†, Dimitri Karamata*
- *Author for correspondence. Tel. +4121206075; fax +4121206078.
- First Published Online: 01 September 1992, Microbiology 138: 1949-1961, doi: 10.1099/00221287-138-9-1949
- Subject: Genetics And Molecular Biology
- Issue Published:
The regulatory unit of Bacillus subtilis strain 168 encompassing the structural genes of the N-acetylmuramoyl-L-alanine amidase and of its modifier has been sequenced, and found to be a divergon consisting of divergently transcribed operons lytABC and lytR. Proteins LytA, LytB and LytC are endowed with export signal peptides. Mature LytA is a 9.4 kDa, highly acidic polypeptide whose deduced amino acid sequence points to a lipoprotein. LytB and LytC, the modifier and the amidase, are highly basic. After cleavage of the signal sequence their molecular masses are 74.1 and 49.9 kDa, respectively. These two proteins share considerable homology in their N-terminal moieties and have three GSNRY consensus motifs, characteristic of nearly all amidases. The C-terminal moiety of LytB exhibits homology to the product of spollD. LytR is a 35 kDa protein which acts as an attenuator of the expression of both lytABC and lytR operons. Transcription of the lytABC operon proceeds from two promoters: PD, identified as P28–7 (Gilman et al., 1984), and an upstream PA. The former only is subject to LytR attenuation. Translational initiation of lytB and lytC is directed by UUG start codons, suggesting that lytA, B and C undergo coupled translation. Transcription of lytR is initiated at two start sites, one of which corresponds to a highly intense PA promoter whereas the other does not seem to share much homology with any of the known promoter consensus sequences. Both promoters are attenuated by LytR. It is confirmed that the synthesis of the amidase is controlled at least in part by SigD, i.e. that it belongs to the fla regulon and that its activity, or part of it, is co-regulated with flagellar motility. The role of the mutations conferring the Sin, Fla and Ifm phenotypes in the expression of the lytABC operon is discussed.
The nucleotide sequence data reported in this paper have been submitted to GenBank and have been assigned the accession number M87645.
Permanent address: Centar za geneticko inzenjerstvo i biotehnologiju, Filipa Kljajica 12, 71000 Sarajevo, Bosnia and Herzegovina.
© Society for General Microbiology, 1992 | Published by the Microbiology Society
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/content/journal/micro/10.1099/00221287-138-9-1949dcterms_title,dcterms_subject-pub_serialIdent:journal/micro AND -contentType:BlogPost104
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