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Infect. Immun., 06 1996, 1929-1936, Vol 64, No. 6
B Gerstel, L Grobe, S Pistor, T Chakraborty and J Wehland
The surface-bound ActA polypeptide of the intracellular bacterial pathogen
Listeria monocytogenes acts as a nucleator protein, generating the actin
cytoskeleton around intracellularly motile bacteria. In this work, we
examined the functional similarity of ActA from Listeria ivanovii (iActA)
ATCC 19119 to its L. monocytogenes counterpart. The amino acid sequence of
iActA predicts a molecular mass of 123 kDa and harbors eight proline-rich
repeats. For functional analysis, various iActA derivatives and hybrid
constructs of L. ivanovii and L. monocytogenes ActA polypeptides were
transiently expressed in epithelial cells and examined for recruitment of
host microfilament proteins by a mitochondrial targeting assay. As has been
demonstrated with ActA, iActA also spontaneously inserted into the surface
of mitochondria and induced recruitment of actin, alpha-actinin, and the
vasodilator-stimulated phosphoprotein (VASP) to these subcellular
organelles. By comparison of amino-terminally truncated iActA derivatives
for their ability to recruit cytoskeletal proteins, a region essential for
actin filament accumulation was identified between amino acid residues 290
and 325. Such derivatives, however, retained their ability to bind VASP.
Replacement of the proline-rich repeats in ActA with those of iActA also
resulted in VASP recruitment. Hence, despite the limited overall sequence
homology between ActA and iActA, the two molecules consist of at least two
similar domains: a highly positively charged N-terminal domain that is
directly involved in actin filament recruitment and a proline-rich repeat
region required for VASP binding.
Copyright © 1996, American Society for Microbiology
The ActA polypeptides of Listeria ivanovii and Listeria monocytogenes harbor related binding sites for host microfilament proteins
Abteilung Zellbiologie and Immunologie, Gesellschaft fur Biotechnologische Forschung, Braunschweig, Germany.
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