ASYMMETRIC DISTRIBUTION OF THE LISTERIA-MONOCYTOGENES ACTA PROTEIN ISREQUIRED AND SUFFICIENT TO DIRECT ACTIN-BASED MOTILITY

Listeria monocytogenes is a Gram-positive facultative intracytoplasmic bacterial pathogen that exhibits rapid actin-based motility in eukary otic cells and in cell-free cytoplasmic extracts. The protein product of the actA gene is required for bacterial movement and is normally ex pressed in a polarized fashion on the bacterial surface. Here we demon strate that the ActA protein is sufficient to direct motility in the a bsence of other L. monocytogenes gene products, and that polarized loc alization of the protein is required for efficient unidirectional move ment. We have engineered a fusion protein combining ActA with the C-te rminal domain of the LytA protein of Streptococcus pneumoniae, which m ediates high-affinity binding to DEAE-cellulose and to choline moietie s present in the S. pneumoniae cell wall. DEAE-cellulose fragments or S. pneumoniae coated uniformly with the ActA/LytA fusion protein nucle ate actin filament growth in cytoplasmic extracts, but do not move eff iciently. However, when ActA/LytA-coated S. pneumoniae is grown to pol arize the distribution of the fusion protein, the bacteria exhibit uni directional actin-based movement similar to the normal movement of L. monocytogenes.