Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.24.55 (PTR)
 433 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

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.
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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 progressive cerebral deposition of a 40-42 residues amyloid beta-peptide (Abeta) is regarded as a major factor in the onset of the Alzheimer's disease. It has recently been shown that Abeta(1-40) is cleaved by Escherichia coli pitrilysin, a homologue of insulysin, at a specific site. To facilitate the studies on a recognition mechanism of Abeta by pitrilysin, an overproduction system of Abeta(1-40) as a fusion protein with E. coli RNase HI was constructed. This fusion protein was designed such that an Abeta(1-40) derivative, Abeta(1-40)*, in which Lys16 and Lys28 of Abeta(1-40) are simultaneously replaced by Ala, is attached to the C-terminus of E. coli RNase HI and Abeta(1-40)* is separated from RNase HI upon cleavage with lysyl endopeptidase. The fusion protein was overproduced in E. coli in inclusion bodies, solubilized and purified in the presence of guanidine hydrochloride, and cleaved by lysyl endopeptidase. Abeta(1-40)* was purified from the resultant peptide fragments by reverse-phase HPLC. Measurement of the far-UV CD spectra suggests that Abeta(1-40)* is conformationally similar to Abeta(1-40). However, the thioflavin T binding assay suggests that Abeta(1-40)* is more amyloidogenic than Abeta(1-40). Nevertheless, Abeta(1-40)* was cleaved by pitrilysin at the site identical to that in Abeta(1-40).
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PMID:Amyloidogenecity and pitrilysin sensitivity of a lysine-free derivative of amyloid beta-peptide cleaved from a recombinant fusion protein. 1623 26

Furan has recently received attention as a possibly hazardous compound occurring in certain thermally processed foods. Previous model studies have revealed three main precursor systems producing furan upon thermal treatment, i.e., ascorbic acid, Maillard precursors, and polyunsaturated lipids. We employed proton transfer reaction mass spectrometry (PTR-MS) as an on-line monitoring technique to study furan formation. Unambiguous identification and quantitation in the headspace was achieved by PTR-MS/gas chromatography-mass spectrometry coupling. Ascorbic acid showed the highest potential to generate furan, followed by glyceryl trilinolenate. Some of the reaction samples generated methylfuran as well, such as Maillard systems containing alanine and threonine as well as lipids based on linolenic acid. The furan yields from ascorbic acid were lowered in an oxygen-free atmosphere (30%) or in the presence of reducing agents (e.g., sulfite, 60%), indicating the important role of oxidation steps in the furan formation pathway. Furthermore, already simple binary mixtures of ascorbic acid and amino acids, sugars, or lipids reduced furan by 50-95%. These data suggest that more complex reaction systems result in much lower furan amounts as compared to the individual precursors, most likely due to competing reaction pathways.
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PMID:Quantitation of furan and methylfuran formed in different precursor systems by proton transfer reaction mass spectrometry. 1656 77

Di- and tripeptide transporters of the PTR/NRT1 (peptide transporter/nitrate transporter1)-family are localized either at the tonoplast (TP) or plasma membrane (PM). As limited information is available on structural determinants required for targeting of plant membrane proteins, we performed gene shuffling and domain swapping experiments of Arabidopsis PTRs. A 7 amino acid fragment of the hydrophilic N-terminal region of PTR2, PTR4 and PTR6 was required for TP localization and sufficient to redirect not only PM-localized PTR1 or PTR5, but also sucrose transporter SUC2 to the TP. Alanine scanning mutagenesis identified L(11) and I(12) of PTR2 to be essential for TP targeting, while only one acidic amino acid at position 5, 6 or 7 was required, revealing a dileucine (LL or LI) motif with at least one upstream acidic residue. Similar dileucine motifs could be identified in other plant TP transporters, indicating a broader role of this targeting motif in plants. Targeting to the PM required the loop between transmembrane domain 6 and 7 of PTR1 or PTR5. Deletion of either PM or TP targeting signals resulted in retention in internal membranes, indicating that PTR trafficking to these destination membranes requires distinct signals and is in both cases not by default.
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PMID:Determinants for Arabidopsis peptide transporter targeting to the tonoplast or plasma membrane. 2253 78

In plants, peptide transporter/nitrate transporter 1 (PTR/NRT1) family proteins transport a variety of substrates such as nitrate, di- and tripepetides, auxin and carboxylates across membranes. We isolated and characterized ZmPTR1, a maize member of this family. ZmPTR1 protein sequence is highly homologous to the previously characterized di- and tripeptide Arabidopsis transporters AtPTR2, AtPTR4 and AtPTR6. ZmPTR1 gene is expressed in the cells of the scutellar epithelium during germination and, to a less extent, in the radicle and the hypocotyl. Arabidopsis thaliana lines overexpressing ZmPTR1 performed better than control plants when grown on a medium with Ala-Ala dipeptide as the unique N source. Our results suggest that ZmPTR1 plays a role in the transport into the embryo of the small peptides produced during enzymatic hydrolysis of the storage proteins in the endosperm.
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PMID:ZmPTR1, a maize peptide transporter expressed in the epithelial cells of the scutellum during germination. 2360 9