AMURAMIDASE IN BRUCELLA ABORTUS IS INVOLVED IN THE EARLY STAGES OF INTRACELLULAR REPLICATION

DEL GIUDICE MG; UGALDE JE; CZIBENER C

Mendoza

Congreso; xLVIII Reunión Anual SAIB; 2012

Argentine Society for Biochemistry and Molecular Biology Research

Secretion of proteins in Gram-negative bacteria is a high-energy consuming process as it requires the translocation across two membranes and the peptidoglycan. To achieve this, bacteria have evolved complex secretion systems that cross these barriers and specific peptidoglycanases that degrade the peptidoglycan to allow the proper assembly of the secretion machinery. Analysis of the genome of Brucella abortus allowed us to identify a gene that we named sagA (Secretion Activator Gene A) coding for a putative lysozyme-like protein. We demonstrated that this protein has peptidoglycanase activity, that a strain with a clean deletion of the gene displayed a defect in the early stages of the intracellular replication in cells and that this is dependent on the lytic activity. While neither the attachment nor the invasion of the strain was affected we showed that the mutant had a defect in excluding the lysosomal marker LAMP-1 but not in acquiring the reticulum endoplasmic marker calnexin, indicating that the gene participates in the early steps of the intracellular trafficking but not in the establishment of the replicative niche. Examination of the genome of B. abortus resulted in the identification of a gene highly similar to sagA , designated sagB, also required during the early stages of intracellular eplication. Our results suggest that these genes do not have redundant functions.