Abstract
1-Naphthylphthalamic acid (NPA) is a specific inhibitor of polar auxin transport that blocks carrier-mediated auxin efflux from plant cells. To allow identification of the NPA receptor thought to be part of the auxin efflux carrier, we have synthesized a tritiated, photolabile NPA analogue, 5'-azido-[3,6-3H2]NPA ([3H2]N3NPA). This analogue was used to identify NPA-binding proteins in fractions highly enriched for plasma membrane vesicles isolated from maize coleoptiles (Zea mays L.). Competition studies showed that binding of [3H2]N3NPA to maize plasma membrane vesicles was blocked by nonradioactive NPA but not by benzoic acid. After incubation of plasma membrane vesicles with [3H2]N3NPA and exposure to UV light, we observed specific photoaffinity labeling of a protein with an apparent molecular mass of 23 kDa. Pretreatment of the plasma membrane vesicles with indole-3-acetic acid or with the auxin-transport inhibitors NPA and 2,3,5-triiodobenzoic acid strongly reduced specific labeling of this protein. This 23-kDa protein was also labeled by addition of 5-azido-[7-3H]indole-3-acetic acid to plasma membranes prior to exposure to UV light. The 23-kDa protein was solubilized from plasma membranes by 1% Triton X-100. The possibility that this 23-kDa polypeptide is part of the auxin efflux carrier system is discussed.
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Claims 9
Claim · model-written summary
A photolabile NPA analogue identified NPA-binding proteins in maize membrane fractions.
Zea maysOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This analogue was used to identify NPA-binding proteins in fractions highly enriched for plasma membrane vesicles isolated from maize coleoptiles (Zea mays L.).”
Claim · model-written summary
Nonradioactive NPA blocked probe binding to maize vesicles.
- Treatment
- nonradioactive NPAe0
- Outcome
- binding of [3H2]N3NPAe0
- Direction
- blockede0
- Comparator
- benzoic acide0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“binding of [3H2]N3NPA to maize plasma membrane vesicles was blocked by nonradioactive NPA but not by benzoic acid.”
Claim · model-written summary
Benzoic acid did not block probe binding.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“binding of [3H2]N3NPA to maize plasma membrane vesicles was blocked by nonradioactive NPA but not by benzoic acid.”
Claim · model-written summary
Photoaffinity labeling identified a 23 kDa protein.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“we observed specific photoaffinity labeling of a protein with an apparent molecular mass of 23 kDa.”
t0“maize”
Claim · model-written summary
Indole-3-acetic acid pretreatment strongly reduced labeling.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Pretreatment of the plasma membrane vesicles with indole-3-acetic acid or with the auxin-transport inhibitors NPA and 2,3,5-triiodobenzoic acid strongly reduced specific labeling of this protein.”
t0“maize”
Claim · model-written summary
NPA pretreatment strongly reduced labeling.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Pretreatment of the plasma membrane vesicles with indole-3-acetic acid or with the auxin-transport inhibitors NPA and 2,3,5-triiodobenzoic acid strongly reduced specific labeling of this protein.”
t0“maize”
Claim · model-written summary
2,3,5-triiodobenzoic acid pretreatment strongly reduced labeling.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Pretreatment of the plasma membrane vesicles with indole-3-acetic acid or with the auxin-transport inhibitors NPA and 2,3,5-triiodobenzoic acid strongly reduced specific labeling of this protein.”
t0“maize”
Claim · model-written summary
The 23-kDa protein was also labeled with the auxin photoprobe.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This 23-kDa protein was also labeled by addition of 5-azido-[7-3H]indole-3-acetic acid to plasma membranes prior to exposure to UV light.”
t0“maize”
Claim · model-written summary
Triton X-100 solubilized the 23-kDa protein from membranes.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The 23-kDa protein was solubilized from plasma membranes by 1% Triton X-100.”
t0“maize”
The same questions in other papers
indole-3-acetic acid · quality: protein · Zea mays (maize)Positive and negative results
1 paper in the same direction as this paper · 1 in the opposite direction
- positive
- negative
Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.