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Department of Cell Biology, Baylor College of Medicine, Houston Texas 77030
We have cloned and
characterized the opt1 gene of
Drosophila melanogaster. This gene
encodes a protein with significant similarity to the PTR family of
oligopeptide transporters. The OPT1 protein is localized to the apical
epithelial membrane domains of the midgut, rectum, and female
reproductive tract. The opt1 message is maternally loaded into developing oocytes, and OPT1 is found in the
-yolk spheres of the developing embryo. It is also found throughout
the neuropil of the central nervous system, with elevated expression
within the
- and
-lobes of the mushroom bodies. Transport activity was examined in HeLa cells transiently expressing OPT1. This
protein is a high-affinity transporter of alanylalanine; the
approximate Km
constant is 48.8 µM for this substrate. OPT1 dipeptide transport
activity is proton dependent. The ability of selected
-lactams to
inhibit alanylalanine transport suggests that OPT1 has a broad
specificity in amino acid side chains and has a substrate requirement
for an
-amino group. Together these data suggest an important role
for OPT1 in regulating amino acid availability.
PTR transport proteins; oligopeptide transport; protein metabolism; yolk; nutrient uptake
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