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At least 19 recordsLinked to original sources
PubMed2003

Isolation and characterization of mutants of the Bacillus subtilis oligopeptide permease with altered specificity of oligopeptide transport.

Bacterial oligopeptide permeases are members of the large family of ATP binding cassette transporters and typically import peptides of 3 to 5 amino acids, apparently independently of sequence. Oligopeptide permeases are needed for bacteria to utilize peptides as nutrient sources and are sometimes involved in signal transduction pathways. The Bacillus subtilis oligopeptide permease stimulates competence development and the initiation of sporulation, at least in part, by importing specific signaling peptides. We isolated rare, partly functional mutations in B. subtilis opp. The mutants were resistant to a toxic tripeptide but still retained the ability to sporulate and/or become competent. The mutations, mostly in the oligopeptide binding protein located on the cell surface, affected residues whose alteration appears to change the specificity of oligopeptide transport.

ATP-Binding Cassette Transporters↗
PubMed1992

Intestinal absorption of beta-lactam antibiotics and oligopeptides. Functional and stereospecific reconstitution of the oligopeptide transport system from rabbit small intestine.

The H(+)-dependent uptake system responsible for the enteral absorption of oligopeptides and orally active beta-lactam antibiotics was functionally reconstituted into liposomes. Membrane proteins from rabbit small intestinal brush border membrane vesicles were solubilized with n-octyl glucoside and incorporated into liposomes using a gel filtration method. At protein/lipid ratios of 1:10 and 1:40, the uptake of the orally active alpha-amino-cephalosporin, D-cephalexin into proteoliposomes was stimulated by an inwardly directed H+ gradient and was protein-dependent. In these proteoliposomes the binding protein for oligopeptides and beta-lactam antibiotics of Mr 127,000 could be labeled by direct photoaffinity labeling with [3H]benzylpenicillin revealing an identical binding specificity as in the original brush border membrane vesicles. The uptake system for beta-lactam antibiotics and oligopeptides showed a remarkable stereospecificity; only D-cephalexin was taken up by intact brush border membrane vesicles, whereas the L-enantiomer was not taken up to a significant extent. This stereospecificity for uptake was also seen after reconstitution of solubilized brush border membrane proteins into liposomes demonstrating a functional reconstitution of the peptide transporter. Both enantiomers however, bound to the 127-kDa binding protein as was shown by a decrease in the extent of photoaffinity labeling of the 127-kDa protein in the presence of both enantiomers. After reconstitution of subfractions of brush border membrane proteins obtained by wheat germ lectin affinity chromatography into proteoliposomes, only liposomes containing the 127-kDa binding protein showed a significant uptake of D-cephalexin whereas the L-enantiomer was not transported. The uptake rates for D-cephalexin into proteoliposomes correlated with the content of 127-kDa binding protein in these liposomes as was determined by specific photoaffinity labeling with [3H]benzylpenicillin. The purified 127-kDa binding protein was also reconstituted into liposomes and its ability for specific binding of substrates as well as stereospecific uptake of cephalexin could be restored. These results indicate that the binding protein for oligopeptides and beta-lactam antibiotics of Mr 127,000 mediates the stereospecific and H(+)-dependent transport of orally active beta-lactam antibiotics across the enterocyte brush border membrane. We therefore suggest that this 127-kDa binding protein is the intestinal peptide transport system (or a component thereof).

Affinity Labels↗
PubMed1986

Molecular recognition between oligopeptides and nucleic acids: novel imidazole-containing oligopeptides related to netropsin that exhibit altered DNA sequence specificity.

Oligopeptides have been synthesized that are structurally related to the antiviral antitumor antibiotic netropsin, but in which each of the pyrrole units is successively replaced by an imidazole moiety, as well as their di- and triimidazole-containing counterparts. These compounds bind to duplex DNA with constants in the range (1.06-1.98) X 10(6) M-1 but not to single-stranded DNA. Since they bind to T4 DNA, it is inferred that, like the parent antibiotic netropsin, they are also minor groove selective. This series of compounds exhibits a progressively decreasing preference for AT sites in binding studies with both native DNAs and synthetic oligonucleotides and a corresponding increasing acceptance of GC base pairs. Footprinting experiments utilizing a 139 base pair HindIII/NciI restriction fragment from pBR 322 DNA revealed that these lexitropsins, or information-reading oligopeptides, recognize more sites than the parent netropsin. In addition, some regions of enhanced nuclease action as the result of drug binding to the fragment were identified. The diimidazole compound in particular recognizes GC-rich sites, implying the formation of new hydrogen bonds between G-C(2)NH2 in the minor groove and the additional N3 imidazole nitrogens. It is clear however that, since the lexitropsins appear to tolerate the original (AT)4 site, an N-methylimidazole group on the ligand will permit either a GC or AT base pair in the binding sequence. Another factor that may be significant in molecular recognition is the high negative electrostatic potential of A X T regions of the minor groove, which is likely to strongly influence binding of these cationic species to DNA.(ABSTRACT TRUNCATED AT 250 WORDS)

Base Sequence↗
PubMed2003

Charged casein-derived oligopeptides competitively inhibit the transport of a reporter oligopeptide by Lactococcus lactis.

AIM: To study the effect of casein-derived peptides, accumulated during growth of Lactococcus lactis in milk, on its oligopeptide transport (Opp) function. METHODS AND RESULTS: This effect was estimated by analysing the ability of casein-derived peptides to compete for the transport of a reporter peptide by whole L. lactis cells. The transport of the reported peptide was monitored by determining the intracellular concentrations of the corresponding amino acids by means of reverse-phase high-performance liquid chromatography (HPLC). Uptake of the reporter peptide was competitively inhibited by casein-derived peptides. The competition was only because of charged casein-derived peptides, including anionic peptides. The design of specific pure peptides made it possible to evidence for a positive (or negative) influence exerted by the positively (or negatively) charged side chain of the N-terminal amino acid on the competition. CONCLUSIONS: Charged casein-derived peptides impaired the oligopeptide transport function of L. lactis. SIGNIFICANCE AND IMPACT OF THE STUDY: These results demonstrate an inhibition of Opp when too many peptides are produced by the proteinase. Peptide transport by Opp therefore represents a bottleneck for increasing the growth rate of L. lactis in milk.

Animals↗
PubMed2001

Three oligopeptide-binding proteins are involved in the oligopeptide transport of Streptococcus thermophilus.

The functions necessary for bacterial growth strongly depend on the features of the bacteria and the components of the growth media. Our objective was to identify the functions essential to the optimum growth of Streptococcus thermophilus in milk. Using random insertional mutagenesis on a S. thermophilus strain chosen for its ability to grow rapidly in milk, we obtained several mutants incapable of rapid growth in milk. We isolated and characterized one of these mutants in which an amiA1 gene encoding an oligopeptide-binding protein (OBP) was interrupted. This gene was a part of an operon containing all the components of an ATP binding cassette transporter. Three highly homologous amiA genes encoding OBPs work with the same components of the ATP transport system. Their simultaneous inactivation led to a drastic diminution in the growth rate in milk and the absence of growth in chemically defined medium containing peptides as the nitrogen source. We constructed single and multiple negative mutants for AmiAs and cell wall proteinase (PrtS), the only proteinase capable of hydrolyzing casein oligopeptides outside the cell. Growth experiments in chemically defined medium containing peptides indicated that AmiA1, AmiA2, and AmiA3 exhibited overlapping substrate specificities, and that the whole system allows the transport of peptides containing from 3 to 23 residues.

Amino Acid Sequence↗
PubMed1991

An oligopeptide permeates intestinal tight junctions at glucose-elicited dilatations. Implications for oligopeptide absorption.

Turnover of the Na(+)-glucose cotransporter in the apical membrane of intestinal absorptive cells elicits alterations in tight-junction structure including the appearance of intrajunctional dilatations. Paralleling these structural responses, epithelial permeability to ions and nutrient-sized solutes increases. However, it is not known how these observed permeability changes specifically relate to the structural alterations elicited by glucose. Using a hemeconjugated peptide tracer (MP-11; mol wt, approximately 1900), the present study shows that the glucose-elicited tight-junction dilatations are specific anatomical sites of junctional permeation. This peptide tracer penetrates tight junctions selectively at sites of dilatations and is detected focally within the paracellular space. This same tracer does not penetrate junctions when glucose is not present. A heme-conjugated macromolecule (horseradish peroxidase; mol wt, approximately 40,000) is excluded by both glucose-exposed and glucose-unexposed tissues. The results of this study show a paracellular pathway for small peptides that is regulated during Na(+)-glucose-activated absorption. It is speculated that the paracellular pathway may contribute to the meal-related oligopeptide absorption that is known to occur and has previously been wholly attributed to the transcellular route.

Amino Acid Sequence↗
PubMed2006

Bacterial beta-peptidyl aminopeptidases with unique substrate specificities for beta-oligopeptides and mixed beta,alpha-oligopeptides.

We previously discovered that BapA, a bacterial beta-peptidyl aminopeptidase, is able to hydrolyze two otherwise metabolically inert beta-peptides [Geueke B, Namoto K, Seebach D and Kohler H-PE (2005) J Bacteriol 187, 5910-5917]. Here, we describe the purification and characterization of two distinct bacterial beta-peptidyl aminopeptidases that originated from different environmental isolates. Both bapA genes encode a preprotein with a signal sequence and were flanked by ORFs that code for enzymes with similar predicted functions. To form the active enzymes, which had an (alphabeta)(4) quaternary structure, the preproteins needed to be cleaved into two subunits. The two beta-peptidyl aminopeptidases had 86% amino acid sequence identity, hydrolyzed a variety of beta-peptides and mixed beta/alpha-peptides, and exhibited unique substrate specificities. The prerequisite for peptides being accepted as substrates was the presence of a beta-amino acid at the N-terminus; peptide substrates with an N-terminal alpha-amino acid were not hydrolyzed at all. Both enzymes cleaved the peptide bond between the N-terminal beta-amino acid and the amino acid at the second position of tripeptidic substrates of the general structure H-betahXaa-Ile-betahTyr-OH according to the following preferences with regard to the side chain of the N-terminal beta-amino acid: aliphatic and aromatic > OH-containing > hydrogen, basic and polar. Experiments with the tripeptides H-d-betahVal-Ile-betahTyr-OH and H-betahVal-Ile-betahTyr-OH demonstrated that the two BapA enzymes preferred the peptide with the l-configuration of the N-terminal beta-homovaline residue as a substrate.

Amino Acid Sequence↗
PubMed1999

The adherence-associated lipoprotein P100, encoded by an opp operon structure, functions as the oligopeptide-binding domain OppA of a putative oligopeptide transport system in Mycoplasma hominis.

Mycoplasma hominis, a cell-wall-less prokaryote, was shown to be cytoadherent by the participation of a 100-kDa membrane protein (P100). To identify the gene encoding P100, peptides of P100 were partially sequenced to enable the synthesis of P100-specific oligonucleotides suitable as probes for the detection of the P100 gene. With this strategy, we identified a genomic region of about 10. 4 kb in M. hominis FBG carrying the P100 gene. Analysis of the complete deduced protein sequence suggests that P100 is expressed as a pre-lipoprotein with a structure in the N-terminal region common to peptide-binding proteins and an ATP- or GTP-binding P-loop structure in the C-terminal region. Downstream of the P100 gene, an additional four open reading frames putatively encoding the four core domains of an active transport system, OppBCDF, were localized. The organization of the P100 gene and oppBCDF in a transcriptionally active operon structure was demonstrated in Northern blot and reverse transcription-PCR analyses, as all gene-specific probes detected a common RNA of 9.5 kb. Primer extension analysis revealed that the transcriptional initiation site was localized 323 nucleotides upstream of the methionine-encoding ATG of the P100 gene. The peptide-binding character of the P100 protein was confirmed by fluorescence spectroscopy and strongly suggests that the cytoadherence-mediating lipoprotein P100 represents OppA, the substrate-binding domain of a peptide transport system in M. hominis.

Amino Acid Sequence↗
PubMed1997

Binding of cationic (+4) alanine- and glycine-containing oligopeptides to double-stranded DNA: thermodynamic analysis of effects of coulombic interactions and alpha-helix induction.

Coulombic interactions and coupled conformational changes make important contributions to stability and specificity of many protein-nucleic acid complexes. As models of these phenomena in simpler systems, we have investigated the binding to mononucleosomal (160 base-pair) calf thymus DNA of a high charge density (compact) 5-residue (+4) oligopeptide (with 4 lysines and 1 tryptophan) and of four lower charge density (extended) 17-residue (+4) oligopeptides (each with 4 lysines, 10-12 alanines, 0-2 glycines, and 1 tryptophan). The fractional helicity (f(h)) of each oligopeptide before and after DNA binding was determined using circular dichroism. At low univalent cation concentration ([M+] = 6.4 mM), binding to DNA increases f(h) significantly for all but one of the extended oligopeptides. Oligopeptide-DNA binding constants (K(obs)) and apparent binding site sizes (n) were quantified using the noncooperative McGhee-von Hippel isotherm to fit tryptophan fluorescence quenching data. For each of the oligopeptides studied, n is found to be approximately equal to four, the number of lysine charges. In the range 6.4 mM < or = [M+] < or = 21.5 mM, power dependences of K(obs) on [M+] (SK(obs) = d log K(obs)/d log[M+]) for all 17-residue (+4) oligopeptides are similar with an average value of -3.7 +/- 0.4, which is indistinguishable (outside uncertainty) from the value obtained here for the compact (+4) oligopeptide and from values reported elsewhere for another compact tetralysine and for spermine (+4). Our results are consistent with the conclusion that the nonspecific binding to DNA of all these tetravalent ligands is driven primarily by coulombic interactions. At any [M+] investigated, values of K(obs) for the four extended (+4) oligopeptides differ by less than an order of magnitude, but all are 1-2 orders of magnitude less than values of K(obs) for two compact (+4) oligopeptides and for spermine. The differences in K(obs) for oligopeptide-DNA complexes, which all have similar n and similar SK(obs) indicate that when an extended oligopeptide binds to DNA it becomes more compact as a result of conformational changes, such as the additional alpha-helix formation detected by circular dichroism.

Alanine↗