Fatty acid synthesis is required for protein translocation during sporulation

VERÓNICA DIEZ,; GUSTAVO E. SCHUJMAN; GUEIROS-FILHO, F; DIEGO DE MENDOZA

Puerto Madryn

Congreso; XLVI Reunión Anual de la Sociedad Argentina de Investigadores en Bioquímica (SAIB); 2010

Sociedad Argentina de Investigadores en Bioquímica (SAIB)

During sporulation in B. subtilis an asymmetrical division creates two compartments, a larger one (mother cell) and a smaller one (prespore). The óE factor is activated only in the mother cell by the membrane protease SpoIIGA which requires SpoIIR, a prespore expressed protein. SpoIIR has a Sec-type signal sequence and is believed to be secreted across the prespore membrane to act as a cell-to-cell signal. We have previously shown that inhibition of fatty acid but not phospholipid biosynthesis prevents óE activation. To study the requirement of fatty acid synthesis on SpoIIR secretion, we examined strains bearing a GFP-SpoIIR fusion during sporulation by fluorescence microscopy. The fusion protein was first concentrated along the septum, but later fluorescence signal accumulated in the prespore cytoplasm suggesting SpoIIR processing. Conversely, cytoplasmic fluorescence was not detected in sporulation arrested cultures, implying an interruption in SpoIIR secretion. Disruption of proteolytic processing was confirmed by western blot using anti-GFP antibodies. Fatty acid synthesis is not a general requirement of protein transport since we found that it is dispensable for secretion of AmyE, another Sec-dependent protein. Together, our results strongly suggest a novel role of de novo fatty acid synthesis on protein membrane translocation during a differentiation process.