1tmq
From Proteopedia
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STRUCTURE OF TENEBRIO MOLITOR LARVAL ALPHA-AMYLASE IN COMPLEX WITH RAGI BIFUNCTIONAL INHIBITOR
Overview
BACKGROUND: alpha-Amylases catalyze the hydrolysis of alpha-D-(1,4)-glucan, linkages in starch and related compounds. There is a wide range of, industrial and medical applications for these enzymes and their, inhibitors. The Ragi bifunctional alpha-amylase/trypsin inhibitor (RBI) is, the prototype of the cereal inhibitor superfamily and is the only member, of this family that inhibits both trypsin and alpha-amylases. The mode of, inhibition of alpha-amylases by these cereal inhibitors has so far been, unknown. RESULTS: The crystal structure of yellow meal worm alpha-amylase, (TMA) in complex with RBI was determined at 2.5 A resolution. RBI almost, completely fills the substrate-binding site of TMA. Specifically, the free, N terminus and the first residue (Ser1) of RBI interact with all three, acidic residues of the active site of TMA (Asp185, Glu222 and Asp287). The, complex is further stabilized by extensive interactions between the enzyme, and inhibitor. Although there is no significant structural reorientation, in TMA upon inhibitor binding, the N-terminal segment of RBI, which is, highly flexible in the free inhibitor, adopts a 3(10)-helical conformation, in the complex. RBI's trypsin-binding loop is located opposite the, alpha-amylase-binding site, allowing simultaneous binding of alpha-amylase, and trypsin. CONCLUSIONS: The binding of RBI to TMA constitutes a new, inhibition mechanism for alpha-amylases and should be general for all, alpha-amylase inhibitors of the cereal inhibitor superfamily. Because RBI, inhibits two important digestive enzymes of animals, it constitutes an, efficient plant defense protein and may be used to protect crop plants, from predatory insects.
About this Structure
1TMQ is a Protein complex structure of sequences from Eleusine coracana and Tenebrio molitor with CL and CA as ligands. Active as Alpha-amylase, with EC number 3.2.1.1 Full crystallographic information is available from OCA.
Reference
A novel strategy for inhibition of alpha-amylases: yellow meal worm alpha-amylase in complex with the Ragi bifunctional inhibitor at 2.5 A resolution., Strobl S, Maskos K, Wiegand G, Huber R, Gomis-Ruth FX, Glockshuber R, Structure. 1998 Jul 15;6(7):911-21. PMID:9687373
Page seeded by OCA on Wed Nov 21 03:25:08 2007
