ISSN:
1399-3054
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Biology
Notes:
The interaction between chloroplast fructose-1,6-bisphosphatase (FBPase) and thioredoxin (Trx) f, two plant proteins involved in the Benson-Calvin cycle, is mainly of an electrostatic nature [Hermoso et al. (1996) Plant Mol Biol 30: 455–465; Reche et al. (1997) Physiol Plant 101: 463–470; Sahrawy et al. (1997) J Mol Biol 269: 623–630; Hermoso et al. (1999) Physiol Plant 105: 756–762], possibly involving carboxyl groups of the enzyme and amino groups of Trx f. We carried out the covalent stabilization of that ionic complex, for the purpose of studying the interaction between both proteins and the factors that influence it. We have used 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide, a reagent able to cross-link carboxyl and amino groups, which allows the formation of covalent bonds between the groups that, in solution, form ionic bonds. A stable functional complex between both proteins was formed. The efficiency in the formation of that complex depends on the redox state of Trx f, ionic strength and pH, showing a strong correlation with the Trx f-dependent enzyme activity. The complex also retains enzyme activity. This suggests that the formation of the covalent complex requires the previous stabilization of a specific functional ionic complex between both proteins, and that in this functional complex carboxyl groups of the enzyme and primary amines of Trx f are involved. This complex is not stable in a tetrameric structure of the enzyme. We could also detect covalent aggregates of FBPase subunits, which indicates the implication of ionic interactions in the stabilization of the tetrameric structure of the enzyme; besides, as molecular filtration experiments and electrophoresis suggest, hydrophobic forces would also be implicated in the enzyme structure.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1034/j.1399-3054.2001.1130403.x
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