First time at Proteopedia? Click on the green links: they change the 3D image. Click and drag the molecules. Proteopedia is a 3D, interactive encyclopedia of proteins, RNA, DNA and other molecules. With a free user account, you can edit pages in Proteopedia. Visit the Main Page to learn more.
|1bya, resolution 2.20Å ()|
CRYSTAL STRUCTURES OF SOYBEAN BETA-AMYLASE REACTED WITH BETA-MALTOSE AND MALTAL: ACTIVE SITE COMPONENTS AND THEIR APPARENT ROLE IN CATALYSIS
The crystal structures of catalytically competent soybean beta-amylase, unliganded and bathed with small substrates (beta-maltose, maltal), were determined at 1.9-2.2-A resolution. Two molecules of beta-maltose substrate bind to the protein in tandem, with some maltotetraose enzymic condensation product sharing the same binding sites. The beta-amylase soaked with maltal shows a similar arrangement of two bound molecules of 2-deoxymaltose, the enzymic hydration product. In each case the nonreducing ends of the saccharide ligands are oriented toward the base of the protein's active site pocket. The catalytic center, located between the bound disaccharides and found deeper in the pocket than where the inhibitor alpha-cyclodextrin binds, is characterized by the presence of oppositely disposed carboxyl groups of two conserved glutamic acid residues. The OE2 carboxyl of Glu 186 is below the plane of the penultimate glucose residue (Glc 2) of bound maltotetraose, 2.6 A from the oxygen atom of that ligand's penultimate alpha-1,4-glucosidic linkage. The OE2 carboxyl of Glu 380 lies above the plane of Glc 2, 2.8 A from the O-1 atom of the more deeply bound beta-maltose. Saccharide binding does not alter the spatial coordinates of these two carboxyl groups or the overall conformation of the 57-kDa protein. However, the saccharide complexes of the active enzyme are associated with a significant (10 A) local conformational change in a peptide segment of a loop (L3) that borders the active site pocket.(ABSTRACT TRUNCATED AT 250 WORDS)
Crystal structures of soybean beta-amylase reacted with beta-maltose and maltal: active site components and their apparent roles in catalysis., Mikami B, Degano M, Hehre EJ, Sacchettini JC, Biochemistry. 1994 Jun 28;33(25):7779-87. PMID:8011643
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
About this Structure
- Mikami B, Degano M, Hehre EJ, Sacchettini JC. Crystal structures of soybean beta-amylase reacted with beta-maltose and maltal: active site components and their apparent roles in catalysis. Biochemistry. 1994 Jun 28;33(25):7779-87. PMID:8011643
- Kang YN, Tanabe A, Adachi M, Utsumi S, Mikami B. Structural analysis of threonine 342 mutants of soybean beta-amylase: role of a conformational change of the inner loop in the catalytic mechanism. Biochemistry. 2005 Apr 5;44(13):5106-16. PMID:15794648 doi:10.1021/bi0476580