1887

Abstract

The molecular basis of protein secretion that underlines rickettsial pathogenesis remains unknown. This paper reports the molecular and functional analysis of the putative gene, an essential component of the Sec-dependent protein secretion pathway, from and , the aetiological agents of Rocky Mountain spotted fever and murine typhus, respectively. The sequence analysis of the cloned genes from and show ORFs of 2721 and 2718 nt, respectively. Alignment of the deduced amino acid sequences reveals the presence of highly conserved amino acid residues and motifs considered to be essential for the ATPase activity of SecA in preprotein translocation. Transcription analysis indicates that is expressed monocistronically from the canonical prokaryotic promoter, with a transcriptional start point located 32 nt upstream of the initiation codon. Complementation analysis shows that the full-length SecA protein from and fails to restore growth of the temperature-sensitive strain MM52 (ts) at a non-permissive temperature (42 °C), despite the detection of SecA protein expression by Western blotting. However, the chimeric SecA protein carrying the N-terminal 408 aa of SecA fused with the C-terminal 480 aa of SecA restores the growth of strain MM52 (ts) at the non-permissive temperature (42 °C). These results suggest that the N-terminal ATPase domain is highly conserved, whereas the C-terminal domain appears to be species specific.

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2005-02-01
2020-04-01
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