Abstract Detail

Biochemistry, metabolism, carbon flux

Liu, Fushan [1], mahkmoudova, Amina [2], Zhao, Qianru [2], Ahmed, Zaheer [2], Tetlow, Ian J. [2], Emes, Michael J. [3].

Protein-protein interactions regulate starch biosynthesis and amylopectin structure.

Starch biosynthesis requires the ordered assembly of glucose units into amylose and amylopectin from ADPglucose. Whilst amylose has a relatively simple linear structure, the synthesis of amylopectin requires the formation of regular, repeating clusters of glucan chains. These clusters have a 9 nm periodicity, and comprise a crystalline, alpha helical, region and an amorphous branched region as unit which is repeated many times over to give rise to blocklets of amylopectin. Although the individual enzymes of starch biosynthesis have been studied extensively, our knowledge of the mechanisms which give rise to this highly ordered structure is limited. There is an increasing body of literature which has demonstrated that several reactions are regulated post-translationally, including via protein-protein interactions and protein phosphorylation, in the endosperm of cereals including wheat, maize, barley and rice, and there is evidence that similar mechanisms operate in the biosynthesis of leaf starch. In this paper we will review the evidence for the formation of heteromeric, multi-enzyme complexes, particularly between isozymes of starch synthases (SS) and starch branching enzymes (SBE) in vitro and in vivo. The consequences of disrupting these interactions on the phenotype of the starch produced will be described. Regulation of protein-protein interactions involves the phosphorylation of starch branching enzymes, starch synthases and starch phosphorylase (SP). Data will be presented on novel, plastid-localized protein kinases which are involved in regulating these protein-protein interactions as well as the biochemical activity of their target enzymes. A model will be presented of how these post-translational mechanisms serve to coordinate the biosynthesis and fine structure of amylopectin in particular.

1 - University of Guelph, Molecular and Cellular Biology, Room 4466, Summerly Science Complex, 488 Gordon Street, Guelph, ON, N1G2W1, Canada
2 - University of Guelph, Miolecular and Cellular Biology, 50 Stone Road East, Guelph, ON, N1G 2W1, CA
3 - University of Guelph, Molecular and Cellular Biology, MCB, Summerlee Science Complex, Guelph, ON, N1G2W1, Canada

Keywords:
Starch Biosynthesis
Amylopectin
protein protein interactions
Biochemistry
Phosphorylation.

Presentation Type: Oral Paper:Papers for Topics
Session: 43
Location: Hall A/The Shaw Conference Centre
Date: Tuesday, July 28th, 2015
Time: 10:15 AM
Number: 43001
Abstract ID:610
Candidate for Awards:None