Study of the enzymes involved in the first steps of phospholipid biosynthesis in Bacillus subtilis

PAOLETTI, L. E.; SCHUJMAN, GE; DIEGO DE MENDOZA,

Rosario

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

SAIB

In E. coli there are two genes, plsB and plsC, that encode for acyltransferases involved in the catalysis of reactions needed for phosphatid acid production. Rock and coworkers demonstrated that in Gram positive bacterial there is a new pathway for the initiation of the phospholipids biosynthesis. The pathway use two enzymes, encode for plsX and plsY genes, in the catalysis of the reaction of acylation of G3P using a new intermediate, fatty acid- phosphate. In B. subtilis there are genes homolog to plsX, plsY and plsC, but no plsB homolog could be identified. To determine the functions of the enzymes encode by plsXb, plsYb and plsCb in B. subtilis, conditional mutants were constructed (LP39, LP61 and LP15 strains). The analysis of the mutants showed that the expression of each gene is essential for the growth of B. subtilis. The analysis of lipids obtained from cultures labeled with [14C] acetate showed that the inducer was depleted the phospholipids biosynthesis was blocked in the three mutants, and fatty acids were accumulated in strain LP15 and LP61. The subcellular localization of PlsXb and PlsCb were analyzed by immunofluorescence microscopy (IFM) and western blot. These experiment showed that PlsCb is localized homogeneously distributed in the cytoplasmic membrane and PlsX is a soluble protein but in vivo is detected in the membrane.  These results suggest that B. subtilis could be using the new pathway for the phospholipids biosynthesis.