In a previous study, we identified additional members of the RTX toxin family, namely, PnxIA and PnxIIA, in P. pneumotropica . Details about their functions and cytotoxicity, excluding their effects on sheep and mouse erythrocytes, remain to be clarified, and it is important to examine these proteins to prove that there are additional genes that code for proteins that are similar to RTX toxins; this is important for elucidating
P. pneumotropica pathogenicity. In this study, we identified a third gene encoding an RTX protein and characterized it in terms of its in vitro cytotoxicity and hemolytic activity. To understand the function of this RTX protein, we attempted to determine its virulence characteristics based CHIR98014 solubility dmso on its predicted primary structure. Results Identification selleck compound of the third gene encoding an RTX protein A previous
study revealed that P. pneumotropica carries 2 genes encoding hemolysin-like proteins that are similar to the RTX toxins PnxIA and PnxIIA . Although both structural protein-coding genes could be detected using Southern hybridization or PCR, several unspecific genes were also detected when the gene coding for PnxIIA was targeted for detection by using PCR techniques in reference strains and wild-type strains of P. pneumotropica (data not shown). In this study, this heterogenic PCR product was cloned, and the inserts of the resultant plasmid pTAC-PX3 were sequenced. The sequence of the inserts was similar to that of the Danusertib cell line glycine-rich regions in pnxIIA; however, the detailed sequence indicated the existence of an additional gene that encodes a protein similar to the RTX toxin. Subsequently, we sequenced the uninserted regions from the genomic DNA of P. pneumotropica ATCC 35149
by using a previously constructed clone library  and inverse PCR. Approximately 14 kb of related genes, including 5 putative open reading frames (ORFs), were finally identified (Figure 1A). To predict the functions of the gene products, the deduced amino acid sequence of each gene was analyzed on the basis of hidden Markov model (HMM) profiles with a protein BLAST search  or the Pfam database . The pnxIII operon comprised the genes encoding 3 functional component proteins, namely, the OmpA-like protein, RTX Thalidomide exoprotein, and type I secretion system component proteins (Figure 1A). The deduced amino acid sequences of tolC, pnxIIIB, and pnxIIID were similar to that of the putative outer membrane (OM) efflux protein of Neisseria sicca ATCC 29256 (GenBank accession no. ZP_05317789) with 68% similarity and 91% coverage, the LapA secretion ATP-binding protein of Neisseria mucosa ATCC 25996 (ZP_05976520) with 86% similarity and 99% coverage, and a membrane fusion protein of Simonsiella muelleri ATCC 29453 (ZP_06753782) with 87% similarity and 100% coverage, respectively.