Characterization of the Streptococcus pneumoniae immunoglobulin A1 protease gene (iga) and its translation product

Abstract

Bacterial immunoglobulin A1 (IgA1) proteases constitute a very heterogenous group of extracellular endopeptidases which specifically cleave human IgA1 in the hinge region. Here we report that the IgA1 protease gene, iga, of Streptococcus pneumoniae is homologous to that of Streptococcus sanguis. By using the S. sanguis iga gene as hybridization probe, the corresponding gene from a clinical isolate of S. pneumoniae was isolated in an Escherichia coli lambda phage library. A lysate of E. coli infected with hybridization-positive recombinant phages possessed IgA1-cleaving activity. The complete sequence of the S. pneumoniae iga gene was determined. An open reading frame with a strongly biased codon usage and having the potential of encoding a protein of 1,927 amino acids with a molecular mass of 215,023 Da was preceded by a potential ؊10 promoter sequence and a putative Shine-Dalgarno sequence. A putative signal peptide was found in the N-terminal end of the protein. The amino acid sequence similarity to the S. sanguis IgA1 protease indicated that the pneumococcal IgA1 protease is a Zn-metalloproteinase. The primary structures of the two streptococcal IgA1 proteases were quite different in the N-terminal parts, and both proteins contained repeat structures in this region. Using a novel assay for IgA1 protease activity upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis, we demonstrated that the secreted IgA1 protease was present in several different molecular forms ranging in size from approximately 135 to 220 kDa. In addition, interstrain differences in the sizes of the pneumococcal IgA1 proteases were detected. Southern blot analyses suggested that the S. pneumoniae iga gene is highly heterogenous within the species.

SpsA, a novel pneumococcal surface protein with specific binding to secretory Immunoglobulin A and secretory component

“…The presence of such repeats indicates that SpsA is a pneumococcal surface protein. The N-terminal part of SpsA with the SC-binding domain exhibits no homology either to pneumococcal IgA1-protease (Poulsen et al, 1996) or to other pneumococcal proteins (Paton et al, 1993). It also showed no homology to IgA-binding proteins from other bacterial species (Lindahl and Ä kerströ m, 1989;Jerlströ m et al, 1991).…”

“…Because of increasing antibiotic resistance among pneumococci and the suboptimal efficacy of polysaccharide vaccine, the interest has shifted towards pneumococcal proteins. Many proteins, such as autolysin (Garcia et al, 1986;Lock et al, 1992), neuraminidase (Berry et al, 1988;Lock et al, 1988), pneumococcal surface adhesin A (PsaA; Sampson et al, 1994), IgA1 protease (Male, 1979;Poulsen et al, 1996), peptide permeases , pneumolysin (Johnson et al, 1980;Paton, 1996) and pneumococcal surface protein A (PspA; Briles et al, 1988; have been identified and characterized. Among these, pneumolysin and PspA have been studied in detail.…”

Pneumococcal zinc metalloproteinase ZmpC cleaves human matrix metalloproteinase 9 and is a virulence factor in experimental pneumonia

“…Two changes have to be made to this nomenclature. The first one concerns SP1154 which is erroneously annotated as Iga-2 although it represents the previously named IgA1-protease gene (Poulsen et al ., 1996;Wani et al ., 1996). SP1154 will therefore be named as IgA1 protease or iga gene throughout the paper.…”

“…Because the only known phenotype for pneumococcal zinc metalloproteinases is the cleavage of human IgA1 (Poulsen et al ., 1996;Wani et al ., 1996), we analysed this feature in our mutants. IgA1 cleavage was assayed by incubating concentrated pneumococcal culture supernatants with human IgA and detecting the size of cleaved or uncleaved IgA1 by Western blot developed with an anti-IgA1 antibody (Fc specific).…”

“…There are two to four surface-located zinc metalloproteinases in Streptococcus pneumoniae . So far human IgA1 is the only substrate demonstrated to be cleaved by one of them (Poulsen et al ., 1996;Wani et al ., 1996;Berge et al ., 2001). As in other oral streptococci, the pneumococcal IgA1 protease is a post-proline endopeptidase, which specifically cleaves the heavy chain of human IgA1 in the hinge region (Senior et al ., 2000).…”