The flagellin subunit of the flagellar filament in Campylobacter jejuni is encoded by two highly homologous tandem genes, flaA and flaB. The flaA gene was sequenced in 18 strains of C. jejuni, including isolates from three outbreak groups. Sequences obtained were compared with flaA sequences available in the GenBank database, and all were analyzed for mosaic gene structure by using recently described statistical tests for detecting gene conversion among aligned sets of sequences. Strong evidence was found supporting recombination between flaA genes of different strains (i.e., intergenomic recombination). Intragenomic recombination between the flaA and flaB genes of C. jejuni TGH9011 was also demonstrated. Both mechanisms of recombination may act as a potential means by which pathogenic strains can generate increased antigenic diversity, so allowing them to escape the immunological responses of the host. Furthermore, demonstration of recombination within and between flagellin loci of natural strains suggests that flagellin gene typing (restriction fragment length polymorphism analysis of PCR-amplified flagellin genes) cannot be considered a stable method for long-term monitoring of pathogenic Campylobacter populations.

Erythromycin-resistant isolates of Streptococcus pneumoniae from blood cultures and noninvasive sites were studied over a 3-year period. The prevalence of erythromycin resistance was 11.9% (19 of 160) in blood culture isolates but 4.2% (60 of 1,435) in noninvasive-site isolates. Sixty-two of the 79 resistant isolates were available for study. The M phenotype was responsible for 76% (47 of 62) of resistance, largely due to a serotype 14 clone, characterized by multilocus sequence typing as ST9, which accounted for 79% (37 of 47) of M phenotype resistance. The ST9 clone was 4.8 times more common in blood than in noninvasive sites. All M phenotype isolates were PCR positive for mef(A), but sequencing revealed that the ST9 clone possessed the mef(A) sequence commonly associated with Streptococcus pyogenes. All M phenotype isolates with this mef(A) sequence also had sequences consistent with the presence of the Tn1207.1 genetic element inserted in the celB gene. In contrast, isolates with the mef(E) sequence normally associated with S. pneumoniae contained sequences consistent with the presence of the mega insertion element. All MLS B isolates carried erm(B), and two isolates carried both erm(B) and mef(E). Fourteen of the 15 MLS B isolates were tetracycline resistant and contained tet(M). However, six M phenotype isolates of serotypes 19 (two isolates) and 23 (four isolates) were also tetracycline resistant and contained tet(M). MICs for isolates with the mef(A) sequence were significantly higher than MICs for isolates with the mef(E) sequence (P < 0.001). Thus, the ST9 clone of S. pneumoniae is a significant cause of invasive pneumococcal disease in northeast Scotland and is the single most important contributor to M phenotype erythromycin resistance.

The complete amino acid sequence (673 residues plus 15 residues of leader sequence) of human complement component C1s has been determined by nucleotide sequencing of cDNA clones from a human liver library probed with synthetic oligonucleotides. Much of the sequence is supported by independent amino acid sequence information. The cDNA sequence contains an anomalous "intron-like" sequence, including a stop codon, that can be discounted because of the amino acid sequence evidence. The N-terminal chain (422 residues) of C1s, like that of C1r with which it is broadly homologous, contains five domains: domains I and III are homologous to one another and to similar regions in C1r, domain II is homologous to the epidermal growth factor sequence found in C1r and several other proteins, and domains IV and V are homologous to one another and to the 60-residue repeating sequence found in C1r, C2, factor B, C4-binding protein and some apparently unrelated proteins. The sequence of the C-terminal chain (251 residues) agrees with that already established to be the "serine protease" domain of C1s.

The complete (17159 bp) nucleotide sequence of the gene for the human C1 inhibitor has been determined. The transcription initiation site was examined by primer extension using human liver mRNA, and the messenger 5'-end sequence was determined on clones obtained by the anchored polymerase chain reaction. The gene of this serpin molecule is split by seven introns, with junctions of phases zero and one. An outstanding feature of the intron sequences is the occurrence of 17 Alul repeats of all four ancestral subgroups, indicating that the gene has been invaded during consecutive waves of A h amplification, including a recent one. These Alu repeats form the sites of deletion and insertion in several known lesions in the C1-inhibitor gene. There is no obvious promoter site of the TATA-box type at the 5' end of the gene, but instead it contains a region of potential H-DNA structure similar to that found upstream of the human c-myc gene.The serine proteinase activity of the activated complement component C1 resides in the two sub-components C l r and Cls [l]. Continuous activation and eventual depletion of the classical complement pathway is prevented by the C1 inhibitor, which is the only plasma inhibitor of C1 [2]. It is able to control C1 activity by binding irreversibly to the active sites of Clr and C1 s [3]. It is also capable of inhibiting other plasma serine proteinases, such as factors XIa and XIIa, plasmin and kallikrein. C1 inhibitor is a single-chain glycoprotein of apparent M , 105000. It contains a large amount of carbohydrate (35%) which does not appear to be necessary for its inhibitory activity [4]. C1 inhibitor cDNA clones have been isolated and sequenced [5 -71. The mature protein contains 478 amino acids which can be divided into two domains. The C-terminal domain of 378 amino acids is homologous to other serine proteinase inhibitors such as a-1-antitrypsin and antithrombin 111, indicating that C1 inhibitor is a member of the serpin superfamily [5 -71. The N-terminal 100 amino acids contain the majority of the 0-and N-linked carbohydrate and show no homology to other serpins [7]. The gene for C1 inhibitor has recently been isolated and the intron-exon structure determined [5]. The protein-coding regions of the gene are divided into seven exons, which are spread over approximately 17 kbp. There is at least one intron in the 5' non-coding region of the gene although the start site of the mRNA has not been determined. Although C1 inhibitor is a member of the serpin Note. The novel nucleotide sequence data published here have been submitted to the EMBL sequence data bank and are available under accession number X54486.Ahhreviations. HANE, hereditary angioneurotic oedema; MeHgOH, methylmercury hydroxide; PCR, polymerase chain reaction; oligo 1 and 2, positions 252-275 and 33-51 respectively of the C1 inhibitor cDNA sequence [7].

Amino acid sequencing of trypsin fragments of C1 inhibitor gave regions of low codon degeneracy that were used for oligonucleotide probes. Human liver cDNA libraries gave clones containing most of the protein sequence, showing that the inhibitory domain belongs to the 'serpin' class of protein inhibitors. Fragments of these cDNA clones were used to probe human genomic cosmid libraries. The genomic sequence was found to be about 17 x lo3 base pairs, with a coding sequence of approximately 1800 base pairs containing introns at amino acid positions -6, 162, 207,275, 321, 395, and one in the 5' non-coding region. There is very little similarity of intron position amongst the serpin genes. All but one of the intron positions in the C1 inhibitor structural gene correspond to surface residues if C1 inhibitor is considered to have a structure similar to the cleaved form of al-antiproteinase. The serine and threonine residues in the N-terminal 100 amino acids of the sequence thought to carry complex carbohydrates are found in a single exon.The first component of complement possesses serine proteinase activity in subcomponents C l r and Cls [l], which is inhibited by the plasma protein known as the C1 inhibitor. This inhibitor is a protein molecule of M , 95 000 which contains about 35% carbohydrate and which forms a stoichiometric complex with the serine proteinase it inhibits [2]. It also inhibits other plasma serine proteinases such as factors XIa and XIIa, plasmin and kallikrein.The functional importance of C1 inhibitor is emphasised by the occurrence of the condition known as hereditary angioneurotic oedema in patients having a genetic abnormality of this molecule. The disease can occur in two main forms: type I, in which the molecule is not expressed by the defective gene, and type 11, in which a molecule of abnormal structure is produced which is immunochemically positive but functionally negative [3].Difficulties of purifying adequate quantities of C1 inhibitor in homogeneous form [4], probably because of the large and variable amount of carbohydrate which contains some sialic acid, have inhibited conventional amino acid sequence studies. Until recently there was remarkably little published amino acid sequence work on C1 inhibitor: the N-terminal 40 residues had been determined [5], and a few residues were known in the 'active-site' region [6]. Sequencing of cDNA clones by Tosi et al. [7] has shown recently that the C-terminal domain is a molecule of the serpin class of proteinase inhibitors. Extensive amino acid sequence results combined with cDNA seauence have recentlv been reDorted bv Bock et al.coding for C1 inhibitor has enabled us to determine the amino acid sequence of the inhibitor protein and to screen human genomic libraries for its gene. Probes prepared from fragments of cDNA clones have allowed us to identify the coding regions of the genomic sequence. DNA sequencing of the genomic clones and comparison with the cDNA sequence has given the location of the intron-exon junctions in the structural gene....

No abstract

A particular recurrent clonal type of Escherichia coliO157 has been isolated from multiple clinical, veterinary, food, and environmental sources throughout Scotland since 1989. Significant genotypic variation was detected among isolates from distinct outbreaks, with the presence or absence of single fragments being sufficient to delineate outbreak groups within the clonal type.

No abstract