Cloning of a second Arabidopsis peptide transport gene.
Previously, we reported the isolation of a peptide transport gene designated AtPTR2 from Arabidopsis thaliana by functional complementation of a yeast peptide transport mutant. We now report the isolation of a second peptide transport gene (AtPTR2-B) from Arabidopsis using the same approach. Similar to the effects of transferring AtPTR2-A (previously called AtPTR2), transfer of AtPTR2-B to yeast peptide transport mutants restored the ability to grow on di- and tripeptides but not peptides four residues or longer. However, unlike yeast mutants complemented with either the yeast PTR2 gene or the AtPTR2-A gene, transformants expressing AtPTR2-B were only partially sensitive to toxic peptides. Northern analysis showed that AtPTR2-B was constitutively expressed in all plant organs. Studies of the kinetics indicated that AtPTR2-A and AtPTR2-B have Km values of 47 and 14 microM, respectively, with Vmax values of 0.061 and 0.013 nmol mg-1 cell dry weight s-1, respectively, when dileucine was used as a substrate. AtPTR2-B is encoded on a 2.0-kb cDNA corresponding to a 585-amino acid protein (64.4 kD). Hydropathy analysis indicates that the protein is highly hydrophobic and suggests that there are 12 putative transmembrane segments. AtPTR2-B, like AtPTR2-A, shares significant similarity to a number of other proteins involved in transport of peptides into cells.
Song
W
W
Department of Microbiology, University of Tennessee, Knoxville 37996-0845, USA.
Steiner
H Y
HY
Zhang
L
L
Naider
F
F
Stacey
G
G
Becker
J M
JM
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics*; D029681:Arabidopsis Proteins; D001692:Biological Transport; D002352:Carrier Proteins / Q000235:genetics*; D004151:Dipeptides / Q000378:metabolism / Q000633:toxicity; D017343:Genes, Plant; D005816:Genetic Complementation Test; D007700:Kinetics; D026901:Membrane Transport Proteins; D015336:Molecular Probe Techniques; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000378:metabolism / Q000633:toxicity; D010455:Peptides / Q000378:metabolism* / Q000633:toxicity; D010940:Plant Proteins / Q000235:genetics*; D012333:RNA, Messenger / Q000032:analysis; D018749:RNA, Plant / Q000032:analysis; D011994:Recombinant Proteins; D012441:Saccharomyces cerevisiae / Q000235:genetics; D017422:Sequence Analysis, DNA
D029681:Arabidopsis Proteins; D002352:Carrier Proteins; D004151:Dipeptides; D026901:Membrane Transport Proteins; D009842:Oligopeptides; C098241:PTR2 protein, Arabidopsis; D010455:Peptides; D010940:Plant Proteins; D012333:RNA, Messenger; D018749:RNA, Plant; D011994:Recombinant Proteins