Abstract
Sucrose synthase (SUS) is phosphorylated on a major, amino-terminal site located at Ser-15 (S15) in the maize (Zea mays) SUS1 protein. Site- and phospho-specific antibodies against a phosphorylated S15 (pS15) peptide allowed direct analysis of S15 phosphorylation in relation to membrane association. Immunoblots of the maize leaf elongation zone, divided into 4-cm segments, demonstrated that the abundance of soluble (s-SUS) and membrane (m-SUS) SUS protein showed distinct positional profiles. The content of m-SUS was maximal in the 4- to 8-cm segment where it represented 9% of total SUS and occurred as a peripheral membrane protein. In contrast, s-SUS was highest in the 12- to 16-cm segment. Relative to s-SUS, m-SUS was hypophosphorylated at S15 in the basal 4 cm but hyperphosphorylated in apical segments. Differing capabilities of the anti-pS15 and anti-S15 peptide antibodies to immunoprecipitate SUS suggested that phosphorylation of S15, or exposure of unphosphorylated SUS to slightly acidic pH, altered the structure of the amino terminus. These structural changes were generally coincident with the increased sucrose cleavage activity that occurs at pH values below 7.5. In vitro S15 phosphorylation of the S170A SUS protein by a maize calcium-dependent protein kinase (CDPK) significantly increased sucrose cleavage activity at low pH. Collectively, the results suggest that (1) SUS membrane binding is controlled in vivo; (2) relative pS15 content of m-SUS depends on the developmental state of the organ; and (3) phosphorylation of S15 affects amino-terminal conformation in a way that may stimulate the catalytic activity of SUS and influence membrane association.
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Claims 9
Claim · model-written summary
Soluble and membrane SUS showed distinct positional profiles in maize leaf elongation zones.
Zea maysNot reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Immunoblots of the maize leaf elongation zone, divided into 4-cm segments, demonstrated that the abundance of soluble (s-SUS) and membrane (m-SUS) SUS protein showed distinct positional profiles.”
t0“maize (Zea mays) SUS1 protein”
Claim · model-written summary
Membrane SUS was maximal at 4 to 8 cm and represented 9% of total SUS.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The content of m-SUS was maximal in the 4- to 8-cm segment where it represented 9% of total SUS and occurred as a peripheral membrane protein.”
t0“maize (Zea mays) SUS1 protein”
Claim · model-written summary
Membrane SUS occurred as a peripheral membrane protein.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“occurred as a peripheral membrane protein”
t0“maize (Zea mays) SUS1 protein”
t1“membrane (m-SUS) SUS protein”
Claim · model-written summary
Soluble SUS was highest in the 12 to 16 cm segment.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“s-SUS was highest in the 12- to 16-cm segment.”
t0“maize (Zea mays) SUS1 protein”
Claim · model-written summary
Membrane SUS was hypophosphorylated at S15 relative to soluble SUS in basal tissue.
- Gene
- S15e0
- Outcome
- m-SUS was hypophosphorylated at S15e0
- Direction
- hypophosphorylatede0
- Qualifier
- basal 4 cme0
- Comparator
- s-SUSe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Relative to s-SUS, m-SUS was hypophosphorylated at S15 in the basal 4 cm but hyperphosphorylated in apical segments.”
t0“maize (Zea mays) SUS1 protein”
Claim · model-written summary
Membrane SUS was hyperphosphorylated at S15 relative to soluble SUS in apical tissue.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Relative to s-SUS, m-SUS was hypophosphorylated at S15 in the basal 4 cm but hyperphosphorylated in apical segments.”
t0“maize (Zea mays) SUS1 protein”
Claim · model-written summary
Antibody immunoprecipitation suggested S15 phosphorylation or acidic pH altered SUS amino-terminal structure.
- Gene
- SUSe0
- Outcome
- structure of the amino terminuse0
- Qualifier
- phosphorylation of S15, or exposure of unphosphorylated SUS to slightly acidic pHe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Differing capabilities of the anti-pS15 and anti-S15 peptide antibodies to immunoprecipitate SUS suggested that phosphorylation of S15, or exposure of unphosphorylated SUS to slightly acidic pH, altered the structure of the amino terminus.”
t0“maize (Zea mays) SUS1 protein”
Claim · model-written summary
Structural changes coincided with increased sucrose cleavage activity below pH 7.5.
- Organ / stage
- amino terminust1
- Outcome
- sucrose cleavage activitye0
- Direction
- increasede0
- Qualifier
- pH values below 7.5e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“These structural changes were generally coincident with the increased sucrose cleavage activity that occurs at pH values below 7.5.”
t0“maize (Zea mays) SUS1 protein”
t1“structure of the amino terminus”
Claim · model-written summary
In vitro S15 phosphorylation significantly increased sucrose cleavage activity of S170A SUS at low pH.
- Treatment
- In vitro S15 phosphorylatione0
- Gene
- S170A SUS proteine0
- Outcome
- sucrose cleavage activitye0
- Direction
- increasede0
- Qualifier
- low pHe0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In vitro S15 phosphorylation of the S170A SUS protein by a maize calcium-dependent protein kinase (CDPK) significantly increased sucrose cleavage activity at low pH.”
The same questions in other papers
in vitro · molecular: metabolites · Zea mays (maize)Positive and negative results
6 papers in the same direction as this paper · 4 in the opposite direction
- negative
- no effect
- negative
7 papers more in this group
See all 11 papers →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.