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Query: EC:3.4.24.55 (PTR)
 433 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

There exist in the Xenopus laevis genome clusters of tandemly repeated DNA sequences, consisting of two types of 393-base-pair repeating unit. Each such cluster contains several units of one of these paired tandem repeats (PTR-1), followed by several units of the other repeat (PTR-2). The number of repeats of each type is variable from cluster to cluster and averages about seven of each type per cluster. Every cluster has ca. 1,000 base pairs of common left flanking sequence (adjacent to the PTR-1 repeats) and 1,000 base pairs of common right flanking sequence (adjacent to the PTR-2 repeats). Beyond these common flanks, the DNA sequences are different in the eight cloned genomic fragments we have studied. Thus, the hundreds of PTR clusters in the genome are dispersed at apparently unrelated sites. Nucleotide sequences of representative PTR-1 and PTR-2 repeats are 64% homologous. These sequences do not reveal an obvious function. However, the related species X. mulleri and X. borealis have sequences homologous to PTR-1 and PTR-2, which show the same repeat lengths and genomic organization. This evolutionary conservation suggests positive selection for the clusters. Maintenance of these sequences at dispersed sites imposes constraints on possible mechanisms of concerted evolution.
Mol Cell Biol 1984 Feb
PMID:Isolated clusters of paired tandemly repeated sequences in the Xenopus laevis genome. 670 May 90

The transport of peptides into cells is a well-documented biological phenomenon which is accomplished by specific, energy-dependent transporters found in a number of organisms as diverse as bacteria and humans. Until recently, the majority of peptide transporters cloned and characterized were found to be proteins of the ATP-binding cassette (ABC) family. We report the identification of a new family of peptide transporters, which we call the PTR family. This group of proteins, distinct from the ABC-type peptide transporters, was uncovered by sequence analyses of a number of recently discovered peptide transport proteins. Alignment of these proteins demonstrated a high number of identical and similar residues and identified conserved glycosylation and phosphorylation sites, as well as a structural motif unique to this group of proteins. Cluster analysis among the proteins indicated these sequences were indeed related and could be further divided into two subfamilies. A phylogenetic analysis of these new peptide transport sequences, compared to over 50 other peptide and membrane-bound transporters, showed that these proteins comprise a distinct, separate group of proteins.
Mol Microbiol 1995 Jun
PMID:The PTR family: a new group of peptide transporters. 747 81

We have isolated and characterized a new alphoid probe, named p190.22. Its chromosomal location was investigated using fluorescence in situ hybridization. Under high stringency conditions p190.22 recognizes specifically the centromere of chromosome 22. A chromosome 22-specific alphoid subset has been previously reported in the literature (p22/1:2.1). The partial sequence and the genomic organization comparison strongly suggests that they recognize distinct subsets both specific for chromosome 22. The comparative mapping of probes p190.22 and p22/1:2.1 on chimpanzee (PTR and PPA) and gorilla (GGO) chromosomes was investigated. The two probes showed different hybridization results. p190.22, in particular, did not show any hybridization signal in these three species, suggesting a recent evolution.
Somat Cell Mol Genet 1994 Sep
PMID:Cloning and comparative mapping of recently evolved human chromosome 22-specific alpha satellite DNA. 782 67

In humans, acute myelomonocytic leukemia (AMML) with abnormal bone marrow eosinophilia is diagnosed by the presence of a pericentric inversion in chromosome 16, involving breakpoints p13;q23 [i.e., inv(16)(p13;q23)]. A pericentric inversion involves breaks that have occurred on the p and q arms and the segment in between is rotated 180 degrees and reattaches. The recent development of a "human micro-coatasome" painting probe for 16p contains unique DNA sequences that fluorescently label only the short arm of chromosome 16, which facilitates the identification of such inversions and represents an ideal tool for analyzing the "divergence/convergence" of the equivalent human chromosome 16 (PTR 18, GGO 17 and PPY 19) in the great apes, chimpanzee, gorilla and orangutan. When the probe is used on the type of pericentric inversion characteristic of AMML, signals are observed on the proximal portions (the regions closest to the centromere) of the long and short arms of chromosome 16. The probe hybridized to only the short arm of all three ape chromosomes and signals were not observed on the long arms, suggesting that a pericentric inversion similar to that seen in AMML has not occurred in any of these great apes.
Mol Gen Genet 1997 Jan 27
PMID:Unique genomic sequences in human chromosome 16p are conserved in the great apes. 903 13

We have isolated and characterized the Saccharomyces cerevisiae PTR3 gene by functional complementation of a mutant deficient for amino acid-inducible peptide transport. PTR3 is predicted to encode a protein of 678 amino acids that exhibits no similarity to any other protein in the database. Deletion of the PTR3 open reading frame pleiotropically reduced the sensitivity to toxic peptides and amino acid analogues. Initial rates of radiolabelled dipeptide uptake demonstrated that elimination of PTR3 resulted in the loss of amino acid-induced levels of peptide transport. PTR3 was required for amino acid-induced expression of PTR2, the gene encoding the dipeptide/tripeptide transport protein, but was not necessary for nitrogen catabolite repression of peptide import or PTR2 expression. It was determined that PTR3 also modulates expression of BAP2, the gene encoding the branched-amino acid permease. Furthermore, we present genetic evidence that suggests that PTR3 functions within a novel regulatory pathway that facilitates amino acid induction of the PTR system.
Mol Microbiol 1998 Jul
PMID:PTR3, a novel gene mediating amino acid-inducible regulation of peptide transport in Saccharomyces cerevisiae. 970 22

The model eukaryote Saccharomyces cerevisiae has two distinct peptide transport mechanisms, one for di-/tripeptides (the PTR system) and another for tetra-/pentapeptides (the OPT system). The PTR system consists of three genes, PTR1, PTR2 and PTR3. The transporter (Ptr2p), encoded by the gene PTR2, is a 12 transmembrane domain (TMD) integral membrane protein that translocates di-/tripeptides. Homologues to Ptr2p have been identified in virtually all organisms examined to date and comprise the PTR family of transport proteins. In S. cerevisiae, the expression of PTR2 is highly regulated at the cellular level by complex interactions of many genes, including PTR1, PTR3, CUP9 and SSY1. Oligopeptides, consisting of four to five amino acids, are transported by the 12-14 TMD integral membrane protein Opt1p. Unlike Ptr2p, distribution of this protein appears limited to fungi and plants, and there appears to be three paralogues in S. cerevisiae. This transporter has an affinity for enkephalin, an endogenous mammalian pentapeptide, as well as for glutathione. Although it is known that OPT1 is normally expressed only during sporulation, to date little is known about the genes and proteins involved in the regulation of OPT1 expression.
Mol Membr Biol
PMID:Multiplicity and regulation of genes encoding peptide transporters in Saccharomyces cerevisiae. 1139 5

A T-DNA tagged mutant line of Arabidopsis thaliana, produced with a promoter trap vector carrying a promoterless gus (uidA) as a reporter gene, showed GUS induction in response to mechanical wounding. Cloning of the chromosomal DNA flanking the T-DNA revealed that the insert had caused a knockout mutation in a PTR-type peptide transporter gene named At5g46050 in GenBank, here renamed AtPTR3. The gene and the deduced protein were characterized by molecular modelling and bioinformatics. Molecular modelling of the protein with fold recognition identified 12 transmembrane spanning regions and a large loop between the sixth and seventh helices. The structure of AtPTR3 resembled the other PTR-type transporters of plants and transporters in the major facilitator superfamily. Computer analysis of the AtPTR3 promoter suggested its expression in roots, leaves and seeds, complex hormonal regulation and induction by abiotic and biotic stresses. The computer-based hypotheses were tested experimentally by exposing the mutant plants to amino acids and several stress treatments. The AtPTR3 gene was induced by the amino acids histidine, leucine and phenylalanine in cotyledons and lower leaves, whereas a strong induction was obtained in the whole plant upon exposure to salt. Furthermore, the germination frequency of the mutant line was reduced on salt-containing media, suggesting that the AtPTR3 protein is involved in stress tolerance in seeds during germination.
J Mol Model 2005 Jun
PMID:Structural and functional characterization of AtPTR3, a stress-induced peptide transporter of Arabidopsis. 1588 94

Two novel metalloproteases from Arabidopsis thaliana, termed AtPrePI and AtPrePII, were recently identified and shown to degrade targeting peptides in mitochondria and chloroplasts using an ambiguous targeting peptide. AtPrePI and AtPrePII are classified as dually targeted proteins as they are targeted to both mitochondria and chloroplasts. Both proteases harbour an inverted metal binding motif and belong to the pitrilysin subfamily A. Here we have investigated the subsite specificity of AtPrePI and AtPrePII by studying their proteolytic activity against the mitochondrial F(1)beta pre-sequence, peptides derived from the F(1)beta pre-sequence as well as non-mitochondrial peptides and proteins. The degradation products were analysed, identified by MALDI-TOF spectrometry and superimposed on the 3D structure of the F(1)beta pre-sequence. AtPrePI and AtPrePII cleaved peptides that are in the range of 10 to 65 amino acid residues, whereas folded or longer unfolded peptides and small proteins were not degraded. Both proteases showed preference for basic amino acids in the P(1) position and small, uncharged amino acids or serine residues in the P'(1) position. Interestingly, both AtPrePI and AtPrePII cleaved almost exclusively towards the ends of the alpha-helical elements of the F(1)beta pre-sequence. However, AtPrePI showed a preference for the N-terminal amphiphilic alpha-helix and positively charged amino acid residues and degraded the F(1)beta pre-sequence into 10-16 amino acid fragments, whereas AtPrePII did not show any positional preference and degraded the F(1)beta pre-sequence into 10-23 amino acid fragments. In conclusion, despite the high sequence identity between AtPrePI and AtPrePII and similarities in cleavage specificities, cleavage site recognition differs for both proteases and is context and structure dependent.
J Mol Biol 2005 Jun 17
PMID:Two novel targeting peptide degrading proteases, PrePs, in mitochondria and chloroplasts, so similar and still different. 1589 67

The integral membrane protein Ptr2p transports di/tri-peptides into the yeast Saccharomyces cerevisiae. The sequence FYXXINXG (FYING motif) in the 5th transmembrane domain (TM5) is invariably conserved among the members of the PTR (Peptide TRansport) family ranging from yeast to human. To test the role of TM5 in Ptr2p function, Ala-scanning mutagenesis of the 22 residues comprising TM5 was completed. All mutated transporters, with the exception of the Y248A mutant, were expressed as determined by immunoblots. In peptide-dependent growth assays, ten mutants of the non-FYING residues grew as well as wild-type Ptr2p on all twelve different peptides tested. All of the FYING motif mutants, except the non-expressed Y248A, plus seven other mutants in TM5 exhibited differential growth on peptides including Leu-Leu and Met-Met-Met indicating that these mutations conferred substrate preference. In assays measuring direct uptake of the radioactive peptides (3)H-Leu-Leu or (14)C-Met-Met-Met, the F, I and G mutants of the FYING motif did not demonstrate accumulation of these peptides over a ten minute interval. The mutation N252A of the FYING motif, along with L240A, M250A, and L258A, exhibited differential substrate preference for Met-Met-Met over Leu-Leu. Other mutations (T239A, Q241A, N242A, M245A, and A260) resulted in preference for Leu-Leu over Met-Met-Met. These data demonstrate that TM5, in particular its conserved FYING motif, is involved in substrate preference of Ptr2p.
Mol Membr Biol
PMID:Substrate preference is altered by mutations in the fifth transmembrane domain of Ptr2p, the di/tri-peptide transporter of Saccharomyces cerevisiae. 1609 64

The transforming growth factor betas (TGFbetas) are context-dependent regulators of neurons in vitro, but their physiological functions in the brain are unclear. Haploinsufficiency of either Tgfbeta1 or Tgfbeta2 leads to age-related deterioration of neurons, but the development of the brain is normal in the full absence of either of these genes. However, some individuals with mis-sense mutations of TGFbeta receptors are mentally retarded, suggesting that the TGFbeta isoforms can compensate for each other during brain development. This possibility was tested by generating mice (NSE x PTR) with neuron-specific expression of a dominant-negative inhibitor of TGFbeta signaling. The NSE x PTR mice with a FVBxC57Bl/6 genetic background were viable and developed normally despite strong neuronal expression of the inhibitor of TGFbeta signaling. Their cerebella were of normal size and contained normal numbers of neurons. When the genetic background of the mice was changed to C57BL/6, the phenotype of the mice became neonatal lethal, with the neonates exhibiting various malformations. The malformations correlated with sites of non-neuronal expression of the transgenes and included facial dysmorphogenesis, incomplete closure of the ventral body wall and absence of intestinal motility. The C57BL/6 Tgfbm1-3 alleles, which modulate the phenotype of Tgfbeta1(-/-) mice, were not major determinants of the NSE x PTR phenotype. The data suggest that the development of the cerebellum is insensitive to the level of TGFbeta signaling, although this may be dependent on the genetic background.
Cell Mol Neurobiol 2009 Jul
PMID:Mice with disrupted TGFbeta signaling have normal cerebella development, but exhibit facial dysmorphogenesis and strain-dependent deficits in their body wall. 1921 40


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