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Structural basis for the interaction between pectin methylesterase and a specific inhibitor protein
Adele Di Matteo1, Alfonso Giovane, Alessandro Raiola
1Department of Biochemical Sciences, University of Rome, 00185 Rome, Italy.
The Plant Cell
|February 22, 2005
Summary
Pectin methylesterases (PMEs) regulate plant development. This study reveals the 3D structure of a tomato PME bound to a kiwi PME inhibitor, clarifying enzyme regulation and inhibitor specificity.
Area of Science:
- Plant biology
- Biochemistry
- Structural biology
Background:
- Pectin is a key plant cell wall component.
- Pectin methylesterases (PMEs) modify pectin.
- PME activity is regulated by protein inhibitors (PMEIs), typically specific to plant PMEs.
Purpose of the Study:
- To determine the 3D structure of a complex between tomato fruit PME and kiwi fruit PMEI.
- To elucidate the molecular basis of PME regulation by PMEI.
- To understand the specificity of PMEIs for plant PMEs.
Main Methods:
- X-ray crystallography at 1.9-A resolution.
- Structural analysis of protein-protein interactions.
Main Results:
- The 3D structure of the tomato PME-kiwi PMEI complex was determined.
- PME exhibits a parallel beta-helical structure; PMEI forms a four-alpha-helix bundle.
- The inhibitor binds to the PME active site cleft in a 1:1 stoichiometric complex.
- Interaction interface is polar, suggesting a nonobligate complex.
Conclusions:
- The structure provides insight into PME regulation by PMEI.
- The findings explain the specificity of PMEIs for plant PMEs.
- This work advances understanding of pectin modification in plants.