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Infection and Immunity, August 2004, p. 4401-4409, Vol. 72, No. 8
0019-9567/04/$08.00+0 DOI: 10.1128/IAI.72.8.4401-4409.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.
Laboratoire de Microbiologie, Institut National de la Santé et de la Recherche Médicale U 411, Faculté de Médecine Necker-Enfants Malades, 75730 Paris Cedex 15,1 Unité des Interactions Bactéries-Cellules,2 Laboratoire de Génomique des Microorganismes Pathogènes,3 Laboratoire des Listeria, Institut Pasteur, 75724 Paris Cedex 15,4 Laboratoire de Microbiologie, Hôpital Raymond Poincaré (Assistance Publique-Hôpitaux de Paris) and EA 3647, Faculté de Médecine Paris-Ile-de-France-Ouest, 92380 Garches, France5
Received 17 November 2003/ Returned for modification 26 February 2004/ Accepted 9 April 2004
Ami is an autolytic amidase from Listeria monocytogenes that is targeted to the bacterial surface via its C-terminal cell wall anchoring (CWA) domain. We recently showed that the CWA domain from Ami of L. monocytogenes EGD (serovar 1/2a) (Ami 1/2a) mediated bacterial binding to mammalian cells. Here we studied the sequence and binding properties of Ami from CHUT 82337 (serovar 4b) (Ami 4b). The Ami 4b polypeptide is predicted to be 770 amino acids long (compared with the 917 amino acids of Ami 1/2a from EGD). Ami 1/2a and Ami 4b are almost identical in the N-terminal enzymatic domain (
98% amino acid identity), but the sequence is poorly conserved in the C-terminal CWA domain, with only
54% amino acid identity and eight GW modules in Ami 1/2a compared with six GW modules in Ami 4b. The purified Ami 4b CWA domain efficiently bound serovar 4b bacterial cells and only poorly bound serovar 1/2a bacterial cells. The Ami 4b CWA domain was also significantly less able to bind Hep-G2 human hepatocytic cells than the Ami 1/2a CWA domain. We sequenced the ami regions encoding CWA domains of reference strains belonging to the 12 L. monocytogenes serovars. The phylogenic tree constructed from the sequences yielded a binary division into group I (serovars 1/2a, 1/2b, 1/2c, 3a, 3b, 3c, and 7) and group II (serovars 4a, 4b, 4c, 4d, and 4e). This is the first direct evidence of divergence between serovars 1/2a and 4b in a gene involved in the adhesion of L. monocytogenes to mammalian cells, as well as the first demonstration of allelic polymorphism correlated with the somatic antigen in this species.
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