Sites of positive and negative regulation in the Bacillus subtilis antiterminators LicT and SacY

Tortosa, P Declerck, N Dutartre, H Lindner, C Deutscher, J Le Coq, D

P. Tortosa et al., Sites of positive and negative regulation in the Bacillus subtilis antiterminators LicT and SacY, MOL MICROB, 41(6), 2001, pp. 1381-1393

50

INGLESE

Article

Microbiology

MOLECULAR MICROBIOLOGY

0950-382X → ACNP

41

6

2001

1381 - 1393

ISI

0950-382X(200109)41:6<1381:SOPANR>2.0.ZU;2-O

The Bacillus subtilis homologous transcriptional antiterminators LicT and S acY control the inducible expression of genes involved in aryl beta -glucos ide and sucrose utilization respectively. Their RNA-binding activity is car ried by the N-terminal domain (CAT), and is regulated by two similar C-term inal domains (PRD1 and PRD2), which are the targets of phosphorylation reac tions catalysed by the phosphoenolpyruvate: sugar phosphotransferase system (PTS). In the absence of the corresponding inducer, LicT is inactivated by BgIP, the PTS permease (Ell) specific for aryl beta -glucosides, and SacY by SacX, a negative regulator homologous to the EII specific for sucrose. L icT, but not SacY, is also subject to a positive control by the general PTS components EI and HPr, which are thought to phosphorylate LicT in the abse nce of carbon catabolite repression. Construction of SacY/LicT hybrids and mutational analysis enabled the location of the sites of this positive regu lation at the two phosphorylatable His207 and His269 within LicT-PRD2, and suggested that the presence of negative charges at these sites is sufficien t for LicT activation in vivo. The BgIP-mediated inhibition process was fou nd to essentially involve His100 of LicT-PRD1, with His159 of the same doma in playing a minor role in this regulation. In vitro experiments indicated that His100 could be phosphorylated directly by the general PTS proteins th is phosphorylation being stimulated by P similar to BgIP. We confirmed that , similarly, the corresponding conserved His99 residue in SacY is the major site of the negative control exerted by SacX on SacY activity. Thus, for b oth antiterminators, the EII-mediated inhibition process seems to rely prim arily on the presence of a negative charge at the first conserved histidine of the PRD1.