A binding-lipoprotein-dependent oligopeptide transport system in Streptococcus gordonii essential for uptake of hexa- and heptapeptides

Abstract

Cells of the oral bacterium Streptococcus gordonii express three cytoplasmic membrane-bound lipoproteins with apparent molecular masses of 76 to 78 kDa that are the products of three genes (designated hppA, hppG, and hppH). The lipoproteins are immunologically cross-reactive, contain 60% or more identical amino acid residues, and are highly similar to the AmiA, AliA (PlpA), and AliB substrate-binding protein components of an oligopeptide permease in Streptococcus pneumoniae. Insertional inactivation of the hppA or hppH gene resulted in loss of the ability of S. gordonii cells to utilize specific peptides of five to seven amino acid residues for growth. An insertion within the COOH-terminal coding region of hppG that caused apparent truncation of the HppG polypeptide had a similar effect; however, S. gordonii mutants in which HppG polypeptide production was abolished were still able to grow on all oligopeptides tested. Inactivation of hppA gene (but not inactivation of the hppG or hppH gene) caused reduced growth rate of cells in complex medium, slowed the rate of development of competence for transformation, reduced the efficiency of transformation, and increased the resistance of cells to aminopterin. These results suggest that the formation of a solute-binding-protein complex consisting of at least the HppA and the HppH lipopolypeptides is necessary for binding and subsequent uptake of primarily hexa-or heptapeptides by a Hpp (Hexa-heptapeptide permease) system in S. gordonii. In addition, Hpp may play a role in the control of metabolic functions associated with the growth of streptococcal cells on complex nitrogen sources and with the development of competence.Binding-protein-dependent transport systems for the uptake of nutrients by bacteria are members of the ubiquitous family of ATP-binding-cassette (ABC)-type transporters (20). The binding-protein-dependent systems are responsible for the transmembrane uptake into bacteria of a wide range of substrates including saccharides, amino acids, peptides, vitamins, anions, and cations (52). The systems consist of one or two transmembrane protein components forming the solute-specific channel, one or two ATP-binding proteins associated with the cytoplasmic side of the membrane, and an extracellular ligand-specific binding protein. The last component is located in the periplasm of gram-negative bacteria, while in grampositive bacteria it is lipid modified and is associated with the external face of the cytoplasmic membrane (51).Uptake systems of this type in bacteria have a wide range of substrate specificities. Some systems have become evolved to transport specific molecules, while others transport a variety of ligands exhibiting similar chemical structures. For the uptake of peptides by bacteria, essentially three ABC-type permeases have been identified that preferentially transport dipeptides, tripeptides, or larger peptides. The dipeptide permease (Dpp) in Escherichia coli and Salmonella typhimurium is a bindingprotein-dependent transport system that transports...

The specificity of oligopeptide transport by Streptococcus thermophilus resembles that of Lactococcus lactis and not that of pathogenic streptococci

“…The partially entrapped peptide is transferred to the transmembrane complex. In S. gordonii, it has been proposed that peptide binding and subsequent uptake require the interaction between two binding proteins, HppA and HppP (Jenkinson et al, 1996). In contrast, interaction between binding proteins is not required for the peptidebinding function in S. pneumoniae: binding proteins are presumably acting independently (Alloing et al, 1994).…”

“…In S. thermophilus ST18, three highly homologous binding proteins (AmiA1, AmiA2 and AmiA3) are associated to a single translocon AmiCDEF. The presence of three distinct binding proteins has also been reported in other streptococci such as Streptococcus gordonii and Streptococcus pneumoniae (Alloing et al, 1994;Jenkinson et al, 1996). Nevertheless, these pathogenic streptococci are reported to transport peptides containing up to nine amino acid residues only.…”

“…The transport system from S. thermophilus consists of several different binding proteins, as in pathogenic streptococci (Alloing et al, 1994;Jenkinson et al, 1996), whereas that of L. lactis has only one binding protein. In each case, the presence of the binding protein is necessary for the transport function.…”

A Multifunction ABC Transporter (Opt) Contributes to Diversity of Peptide Uptake Specificity within the Genus Lactococcus

“…The Opt proteins exhibit the highest identities with the corresponding Opp proteins from Streptococcus mutans UA159 (1). Similarly, OptA exhibits higher identities with streptococcal OBPs than with OppA proteins from Lactococcus or Lactobacillus species (4, 27): 48.5, 32.0, 30.0, 31.2, and 28.4% identities were observed with OppA2 from Streptococcus uberis 0140J, AmiA and AliB from Streptococcus pneumoniae R800, HppA from Streptococcus gordonii DL1, and AmiA1 from S. thermophilus St18, respectively (2,11,19,35). OptA (545 aa) and OptS (549 aa) are very short OBPs.…”

Characterization of a copper-transport operon, copYAZ, from Streptococcus mutans The GenBank accession number for the cop operon sequence reported in this paper is AF296446.

“…The 4 kb HindIII (blunted with Klenow)-XbaI fragment from pHTL1 was isolated and ligated to a 6n5 kb fragment of pSL2 generated by digestion with BamHI (followed by Klenow treatment) and XbaI. Plasmid pSL2 was constructed in our laboratory and contained a 0n4 kb DNA fragment encoding a non-essential oligopeptide-transport gene (hppG) originating from Streptococcus gordonii DL1 (Jenkinson et al, 1996). Plasmid pSL2 also carried a 1n5 kb fragment of the spaP gene which encodes the major surfaceprotein antigen (P1) of Strep.…”