Comparative sequence analysis of the icm/dot genes in Legionella.
The icm/dot genes in Legionella pneumophila are essential for the ability of the bacteria to survive within macrophages in lung infections such as Legionnaires' disease, or amoebae in nature. The 22 genes of the complex, thought to encode a transport apparatus for transfer of effector molecules into the host cell cytoplasm, are located in two chromosomal loci. We demonstrate that these genes are present in all the L. pneumophila strains examined herein, but display a wide range of sequence variation among the different strains, none of which are clearly associated with virulence potential. The strains fall within seven phylogenetic groups, but discrepancies among the gene trees indicate a complicated evolutionary history for the icm/dot loci, with perhaps two independent gene acquisition events and subsequent genomic rearrangements. Significant findings include a probable t-SNARE domain in IcmG that may indicate a direct role for this putative inner membrane protein in altering the host's membrane fusion machinery, a potential functional domain in the central hydrophobic portion of IcmK that may allow it to participate in forming the pore of the secretion complex, and strict conservation of the amino acid physicochemical characteristics in the IcmP region corresponding to the trbA domain that could play a role in molecular transfer.
Columbia Genome Center, Columbia University College of Physicians and Surgeons, 1150 St. Nicholas Avenue, New York, NY 10032, USA.
Irina
I
Morozova
Xiaoyan
X
Qu
Shundi
S
Shi
Gifty
G
Asamani
Joseph E
JE
Greenberg
Howard A
HA
Shuman
James J
JJ
Russo
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics*; D001483:Base Sequence; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D019143:Evolution, Molecular; D016952:Legionella pneumophila / Q000737:chemistry / Q000235:genetics*; D008969:Molecular Sequence Data; D009693:Nucleic Acid Hybridization; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D012336:RNA, Ribosomal, 16S / Q000737:chemistry / Q000235:genetics; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D014774:Virulence
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D012336:RNA, Ribosomal, 16S