Role of lipids in the activation of sigE factor during the sporulation in Bacillus subtilis

VERÓNICA DIEZ,; SCHUJMAN, GE; DE MENDOZA, D

Rosario

Congreso; XLII Reunión Anual de la Sociedad Argentina de Investigadores en Bioquímica (SAIB); 2006

SAIB

In the absence of nutrients B. subtilis initiates a differentiation process called sporulation. After an asymmetrical division two compartments are created, the larger one called mother cell and the smaller one, the prespore. sE factor, which is essential for sporulation, is proteolitically activated only in the mother cell by the membrane protease SpoIIGA which requires SpoIIR, a protein synthestized in the prespore. We have previously shown that inhibition of fatty acid biosynthesis by addition of the antibiotic cerulenin at the onset of sporulation precludes sE activation, which blocks the differentiation process. To understand at which step of sE activation lipids are required, we constructed a version of SpoIIR lacking its signal sequence and found that translocation of SpoIIR is not necessary for SpoIIGA activity when both proteins are expressed in the same compartment. The analysis of the sporulation frequency of mixed cultures of spoIIR and spoIIGA mutant strains in the presence and absence of cerulenin suggested that lipids are required for SpoIIR translocation or its interaction with the protease. Finally, we analyzed sE activation in a plsC conditional mutant. In this strain, phospholipid biosynthesis is blocked and fatty acids are accumulated. Our experiments indicated that fatty acid and not phospholipids biosynthesis is essential for sE activation.