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Interspecies sequence differences in the Mip protein from the genus Legionella: implications for function and
R M Ratcliff1, S C Donnellan, J A Lanser
1Infectious Diseases Laboratories, Institute of Medical and Veterinary Science, Adelaide, South Australia. rratclif@microb.adelaide.edu.au
Molecular Microbiology
|November 14, 1997
Summary
The mip gene sequences from 35 Legionella species show high conservation, particularly in functional domains. This suggests Mip protein function is similar across species, regardless of disease association or environmental origin.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- The macrophage infectivity potentiator (Mip) protein is crucial for Legionella pathogenesis.
- Understanding Mip gene and protein sequence variation is key to deciphering Legionella virulence and evolution.
Purpose of the Study:
- To analyze the nucleotide and amino acid sequence conservation of the mip gene across 35 Legionella species.
- To investigate potential functional differences in Mip protein based on sequence analysis.
- To perform phylogenetic analysis of Legionella species using mip and 16S rRNA sequences.
Main Methods:
- Nucleotide and amino acid sequencing of mip genes from 35 Legionella species.
- Sequence comparison with existing data for L. pneumophila, L. micdadei, and L. longbeachae.
- Phylogenetic analysis using both genetic distance and maximum parsimony methods on mip and 16S rRNA sequences.
Main Results:
- Mip sequences exhibited high conservation: 69-97% at the nucleotide level and 82-99% at the amino acid level.
- Conserved amino acids were located in regions critical for peptidyl prolyl cis-trans isomerase activity.
- No sequence-based functional differences were identified between Mip from pathogenic and non-pathogenic Legionella species.
- Phylogenetic analysis revealed limited consensus between mip and 16S rRNA trees, with one robust clade identified.
Conclusions:
- The Mip protein is highly conserved across Legionella species, indicating a conserved function essential for the genus.
- Sequence analysis does not predict functional divergence of Mip related to pathogenicity.
- Phylogenetic relationships derived from mip sequences offer a complementary view to 16S rRNA-based phylogenies.