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Title: THE ASSOCIATION OF SUCROSE SYNTHASE WITH INTRACELLULAR MEMBRANES MAY INVOLVE A REGION WITH SIMILARITY TO A PLECKSTRIN HOMOLOGY DOMAIN.

Author
item HARDIN, SHANE - UNIVERSITY OF ILLINOIS
item DUNCAN, KATERI - UNIVERSITY OF ILLINOIS
item Huber, Steven

Submitted to: Plant Biology Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 4/7/2005
Publication Date: 5/1/2005
Citation: Hardin, S.C., Duncan, K.A., Huber, S.C. 2005. The association of sucrose synthase with intracellular membranes may involve a region with similarity to a pleckstrin homology domain [abstract]. Plant Biology Annual Meeting. Available: http://abstracts.aspb.org/pb2005/public/P56/7488.html.

Interpretive Summary:

Technical Abstract: Sucrose synthase (SUS) is associated with the plasma membrane, where it is thought to provide UDP-glucose for cellulose biosynthesis. The mechanisms involved in directing this soluble, globlular enzyme to cellular membranes are unknown. We are studying the structural requirements for interaction of maize SUS1 with membranes using a series of MBP-tagged truncation mutants of SUS1. Binding of the truncations to bacterial membranes implicated a region of about 100 amino acids that has primary sequence similarity to the C-terminal PH-domain found in human pleckstrin, which is known to interact with membranes. Site-directed alanine substitution mutants are being used to assess the contribution of individual amino acids within the putative PH-domain of SUS1 to membrane binding. Interestingly, removal of the C-terminal non-catalytic domain (74 amino acids) of SUS1 resulted in increased membrane binding relative to the full-length construct, implying a negative regulatory role for this region. Binding of full-length SUS1 to maize leaf-derived microsomes showed positive cooperativity with increasing protein concentration and was also stimulated by sugars, including those that are not recognized at the catalytic site, suggesting that a regulatory sugar-binding site was involved. This observation suggests that sugar-sensing by this enzyme could regulate the diversion of carbon from sucrose towards cellulose synthesis only when excess photosynthate is available. Our goal is to identify SUS1 mutants that affect membrane binding (either promote or disrupt) but not enzymatic activity, in order to potentially influence the in plantachanneling of carbon to cell wall glucans.