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. 1996 Dec 10;93(25):14648-53.
doi: 10.1073/pnas.93.25.14648.

"VSports最新版本" cag, a pathogenicity island of Helicobacter pylori, encodes type I-specific and disease-associated virulence factors

S Censini  1 , C Lange, Z Xiang, J E Crabtree, P Ghiara, M Borodovsky, R Rappuoli, A Covacci
Affiliations

cag, a pathogenicity island of Helicobacter pylori, encodes type I-specific and disease-associated virulence factors

"VSports" S Censini et al. Proc Natl Acad Sci U S A. .

"V体育官网入口" Abstract

cagA, a gene that codes for an immunodominant antigen, is present only in Helicobacter pylori strains that are associated with severe forms of gastroduodenal disease (type I strains). We found that the genetic locus that contains cagA (cag) is part of a 40-kb DNA insertion that likely was acquired horizontally and integrated into the chromosomal glutamate racemase gene. This pathogenicity island is flanked by direct repeats of 31 bp. In some strains, cag is split into a right segment (cagI) and a left segment (cagII) by a novel insertion sequence (IS605). In a minority of H. pylori strains, cagI and cagII are separated by an intervening chromosomal sequence VSports手机版. Nucleotide sequencing of the 23,508 base pairs that form the cagI region and the extreme 3' end of the cagII region reveals the presence of 19 ORFs that code for proteins predicted to be mostly membrane associated with one gene (cagE), which is similar to the toxin-secretion gene of Bordetella pertussis, ptlC, and the transport systems required for plasmid transfer, including the virB4 gene of Agrobacterium tumefaciens. Transposon inactivation of several of the cagI genes abolishes induction of IL-8 expression in gastric epithelial cell lines. Thus, we believe the cag region may encode a novel H. pylori secretion system for the export of virulence determinants. .

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Figure 1
Figure 1
Schematic representation of the cag region as deduced from analysis of strain CCUG 17874. The cag integration site within the glutamate racemase gene (glr) is shaded (a). cag structure: the putative ORFs are represented by arrows (b). Flanking the intervening sequence (dots), the IS605 have a left and right end indicated with large solid and open arrowheads. ORFs with strong similarity are indicated. The cagII region is drawn interrupted but ordered clones and long distance PCR give an approximate indication of the total length, which is indicated by a continuous line. The results of amino acid database searches are included. The name of the genes are in boldface type. LLS, low level of similarity (e−2 > e > e−10); HLS, high level of similarity (>e−50). GenBank, EBI, Swiss-Prot, and Protein Identification Resource releases for December 31, 1995 were used. cagT (LLS), Shigella flexnerii 42-kDa surface antigen IPAC_SHIFL; membrane protein P60 Mycoplasma hominis S42614; Plasmodium falciparum 10b antigen (asparagine rich) J03986 (prokaryotic lipoprotein membrane attachment site). cagS (LLS), Erwinia chrysantemi IIABC component PTS system PTBA_ERWCH; Clostridium perfringens transposase for IS115 TRA1_CLOPE·tnpA (HLS), IS200 from E. coli, S. typhimurium, and Yersinia pestis L25848, U22457, and L25845; S. typhimurium plasmid pSDL2/spvD26 (vsdA–F genes for virulence proteins) X56727. tnpB (HLS), thermophilic bacterium PS3 gene for transposase-like protein D38778; S. typhimurium virulence protein vsdF P24421P24421. cagR (LLS), preprotein translocase secY subunit SECY_STACA; polysialic acid transport protein KPSM_ECOLI; cagQ (LLS) Neisseria gonorrhoeae prepilin peptidase P33566; glutamate/aspartate transporter E. coli GLTJ_ECOLI; 42-kDa membrane antigen precursor Shigella IPAC_SHIFL. cagP (LLS), fimbrial assembly protein (serogroup I) Fmbi_BACNO; type 4 prepilin-like protein-specific leader peptidase LEP3_PSEAE; hydrophobic membrane protein Haemophilus U32720. cagO (LLS), transport system permease P69_Mychr; polysialic acid transporter E. coli KPSN_ECOLI; NADH-ubiquinone oxidoreductase chain 5 (also chain 1, 2) NU1M_ASCSU. cagM (LLS), hook-associated protein type 3 U12817; merozoite surface antigen PFMEZSA1A_1. cagN (LLS), Lmp 1 M. hominis U21963; acidic basic repeat antigen P. falciparum A12521; α-cardiac myosin hc M76598. cagL (LLS), preprotein translocase SECA_ANTSP; proteases secretion protein PRTE_ERWCH. cagI (LLS), CFA/I fimbrial subunit D CFAD_ECOLI; FlaB C. coli A35146;Treponema membrane protein precursor P29721. cagH (LLS), extracellular protease precursor PROA_XANCP; GSP protein d precursor Erwinia chrisantemi GSQD_ERWCH;Treponema membrane protein precursor P29721. cagG (LLS), flagellar motor switch protein FLIM_CAUCR; toxin coregulated pilus biosynthesis protein D (TCP pilus biosynthesis protein TCPD)_VIBCH; GSP protein d precursor Erwinia chrisantemi GSPD_ERWCH. cagF (LLS), ToxB, ToxA_CLODI. cagE (HLS), VirB4 homolog_BPERT (ptlc); VirB4 homolog (plasmid pTiA6)_AGRT9; TraB of IncN plasmid pKM101; TrbE (Tra2 region) of IncP plasmid RP4 (Walker box). cagD (LLS), flagellar hook-associated protein 2 (filament cap) FLID_SALTY; surface presentation SPAO_SHIFL. cagC (LLS), TRAH protein precursor TRH1_ECOLI; SECE_ECOLI protein-export (preprotein translocase); 62-kDa membrane antigen IPAB_SHIDY; sensor protein ENVZ_SALTY. cagB (LLS), sensor protein UHPB_ECOLI; hypothetical 16.6-kDa protein outside the virF region (ORF3)_AGRT9; BACN17G_7 hypothetical protein BACSU; transport system permease protein p69_MYCHR. glr (HLS), glutamate racemase LEPRAE_BREVIS_COLI. Coordinates, headers, and comments are included in the submitted sequence.
Figure 2
Figure 2
(A) Sequences of the left (L) and right (R) end of IS605 (1) and is605 (2) and the general structure of both elements. The core is formed by a conserved hexanucleotide, inscribed into a circle. The arrows indicate the dyadic structure of the ends. Astericks are nonconserved nucleotides. The sequences included in the boxes are specular. The last 31 bp of glutamate racemase gene, representing the duplicated sequence, are shown (3). The core is marked. Stop is the stop codon of glutamate racemase gene. Coordinates are relative to the cag nucleotide sequence. (B) Summarizes the structure of cag in a collection of strains previously described (4). cag is represented by a horizontal white bar (1). IS605 (2 and 3) and the intervening sequence (3) are indicated as in Fig. 1.
Figure 4
Figure 4
Evolutionary tree that describes the hypothetical emergence of H. pylori type I as a result of an event of gene conversion (PAI acquisition). Presumably, it is only after the integration of an IS605 that subpopulations of intermediate strains with attenuated virulence are differentiated. cag retention is indicated by arrows. Type II strains are distinguishable from type I strains with a complete cag deletion by the absence of IS605. The following strains have the genotypes listed in the tree. Genotypes: 1, G11, G33, G46, G89, G103, G109, 932, Ba99, Ba 137, and Ba158; 2, CCUG 17874, G32, G56, G106, and G204; 3, 60190, G20, G27, G29, G65, Ba179, and Ba 211; 4, G39, D933, Ba167, Ba182, Ba194, and Ba212; 5, G12 and G25; 6, G104 and D925; 7, Tx30a and G50; 8, Ba82, Ba142, G21, G198, 2U+, and 2U-.
Figure 3
Figure 3
Schematic diagram indicating the IL-8 secretion from KATO-III gastric epithelial cells induced by different mutants as compared with the parenteral strain G27. Mutants are single gene inactivation by mini-Tn3 insertion and are indicated by the name of the affected ORF. A type II strain is included as a negative control. The results represent the mean (SEM) of 7–11 experiments.
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