A point mutation in the active site of Legionella pneumophila O-acetyltransferase results in modified lipopolysaccharide but does not influence virulence

Citation
Cp. Luck et al., A point mutation in the active site of Legionella pneumophila O-acetyltransferase results in modified lipopolysaccharide but does not influence virulence, INT J MED M, 291(5), 2001, pp. 345-352
Citations number
39
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Microbiology
Journal title
INTERNATIONAL JOURNAL OF MEDICAL MICROBIOLOGY
ISSN journal
1438-4221 → ACNP
Volume
291
Issue
5
Year of publication
2001
Pages
345 - 352
Database
ISI
SICI code
1438-4221(200111)291:5<345:APMITA>2.0.ZU;2-1
Abstract
The majority of clinical isolates of Legionella pneumophila serogroup 1 pro duce lipopolysaccharide (LPS) that reacts with monoclonal antibody (MAb) 3/ 1. By using a negative cell sorting method, we isolated a spontaneous LPS m utant from L. pneumophila serogroup I strain Corby that lost reactivity wit h this MAb. The mutant contained a single nucleotide exchange in position 1 69 of the lag-1 gene that encodes an O-acetyltransferase that is responsibl e for O-acetylation of the L. pneumophila O-repeat unit (legionaminic acid) . This mutation resulted in a single amino acid exchange in a highly conser ved motif present in many O-acetyltransferase-like proteins. RT-PCR analysi s revealed that the mutant lag-1 gene was transcribed, but the resulting pr otein lacked O-acetyltransferase activity. Chemical analysis of the mutant LPS revealed that it lacked 8-O-acetyl groups in legionaminic acid. In addi tion, the mutant failed to produce high-molecular-weight long-chain O-polys accharide. Complementation of the mutant with the wild-type lag-1 gene rest ored reactivity with MAb 3/1 and the chemical structure of the wild-type LP S. Strain Corby and its MAb 3/1-negative mutant were indistinguishable in t heir serum resistance characteristics, and in uptake and intracellular mult iplication in Acanthamoeba castellanii and macrophages.