Molecular analysis of an A-protein secretion mutantof Aeromonas salmonicida reveals a surface layer-specific protein secretion pathway

摘要: The Aeromonas salmonicida Tn5 mutant, A449-TM1, is unable to secrete thesurface layer protein (A-protein) through the outer membrane. Immunogold labeling of thin sections with polyclonal antisera against A-protein, showed accumulation large quantities A-protein in an enlarged periplasm. majority labeled could be seen at poles cells. ability A449-TM1 other extracellular proteins such as hemolysin and protease was not impaired by insertion, which indicates that mutation interferes a secretion pathway specifically for translocation shown avirulent fish. A cosmid clone from gene library contains insertion chromosome, used identify 1.4 kb SaII/ClaI fragment immediately adjacent insertion. This 4 HindIII chromosomal DNA digest wild-type strain, A449. sequence analysis this identified open reading frame (ORF) 1656 bp. deduced product ORF similarity family ATP-binding proteins, but appeared phylogenetically distinct these consistent its participation secretory specific surface protein.