4HLN

Structure of barley starch synthase I in complex with maltooligosaccharide

Summary for 4HLN

• Entry DOI: 10.2210/pdb4hln/pdb
• Related PRD ID: PRD_900030
• Descriptor: Starch synthase I, alpha-D-glucopyranose-(1-4)-alpha-D-glucopyranose-(1-4)-alpha-D-glucopyranose-(1-4)-alpha-D-glucopyranose-(1-4)-alpha-D-glucopyranose (3 entities in total)
• Functional Keywords: double rossmann fold, glycosyltransferase, adpglucose, maltooligosaccharide, glycogen, amylopectin, disulfide, plastidial, transferase
• Biological source: Hordeum vulgare (barley)
• Total number of polymer chains: 1
• Total formula weight: 70725.84

Authors

Cuesta-Seijo, J.A.,Nielsen, M.M.,Marri, L.,Tanaka, H.,Palcic, M.M. (deposition date: 2012-10-17, release date: 2013-06-05, Last modification date: 2024-11-20)

Primary citation

Cuesta-Seijo, J.A.,Nielsen, M.M.,Marri, L.,Tanaka, H.,Beeren, S.R.,Palcic, M.M.
Structure of starch synthase I from barley: insight into regulatory mechanisms of starch synthase activity
Acta Crystallogr.,Sect.D, 69:1013-1025, 2013

PubMed Abstract: Starch, a polymer of glucose, is the major source of calories in the human diet. It has numerous industrial uses, including as a raw material for the production of first-generation bioethanol. Several classes of enzymes take part in starch biosynthesis, of which starch synthases (SSs) carry out chain elongation of both amylose and amylopectin. Plants have five classes of SS, each with different roles. The products of the reaction of SS are well known, but details of the reaction mechanism remain obscure and even less is known of how different SSs select different substrates for elongation, how they compete with each other and how their activities are regulated. Here, the first crystal structure of a soluble starch synthase is presented: that of starch synthase I (SSI) from barley refined to 2.7 Å resolution. The structure captures an open conformation of the enzyme with a surface-bound maltooligosaccharide and a disulfide bridge that precludes formation of the active site. The maltooligosaccharide-binding site is involved in substrate recognition, while the disulfide bridge is reflective of redox regulation of SSI. Activity measurements on several SSI mutants supporting these roles are also presented.

PubMed: 23695246
DOI: 10.1107/S090744491300440X

Experimental method

X-RAY DIFFRACTION (2.7 Å)