tailieunhanh - Báo cáo khoa học: The starch-binding capacity of the noncatalytic SBD2 region and the interaction between the N- and C-terminal domains are involved in the modulation of the activity of starch synthase III fromArabidopsis thaliana

Starch synthase III from Arabidopsis thaliana contains an N-terminal region, including three in-tandem starch-binding domains, followed by a C-terminal catalytic domain. We have reported previously that starch-bind-ing domains may be involved in the regulation of starch synthase III func-tion. | The starch-binding capacity of the noncatalytic SBD2 region and the interaction between the N- and C-terminal domains are involved in the modulation of the activity of starch synthase III from Arabidopsis thaliana Enzymes and catalysis Nahuel Z. Wayllace1 2 Hugo A. Valdez1 Rodolfo A. Ugalde1 f Maria V. Busi1 2 and Diego F. Gomez-Casati1 2 1 Institute de Investigaciones Biotecnologicas-Instituto Tecnologico de Chascomus Argentina 2 Centro de Estudios Fotosinteticos y Bioquimicos Universidad Nacionalde Rosario Argentina Keywords Arabidopsis enzyme regulation protein interaction starch synthase starch-binding domain Correspondence D. F. Gomez-Casati Centro de Estudios Fotosinteticos y Bioquimicos CEFOBI-CONICET Universidad Nacionalde Rosario Suipacha 531 2000 Rosario Argentina Fax 54 341 437 0044 Tel 54 341 437 1955 E-mail gomezcasati@ fDeceased Received 14 September 2009 revised 10 November 2009 accepted 13 November 2009 doi Starch synthase III from Arabidopsis thaliana contains an N-terminal region including three in-tandem starch-binding domains followed by a C-terminal catalytic domain. We have reported previously that starch-binding domains may be involved in the regulation of starch synthase III function. In this work we analyzed the existence of protein interactions between both domains using pull-down assays far western blotting and co-expression of the full and truncated starch-binding domains with the catalytic domain. Pull-down assays and co-purification analysis showed that the D 316-344 and D 495-535 regions in the D2 and D3 domains respectively but not the individual starch-binding domains are involved in the interaction with the catalytic domain. We also determined that the residues W366 and Y394 in the D2 domain are important in starch binding. Moreover the co-purified catalytic domain plus site-directed mutants of the D123 protein lacking these aromatic residues showed that W366 was key to the .

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