The structure of barley alpha-amylase isozyme 1 reveals a novel role of domain C in substrate recognition and binding: a pair of sugar tongs.
Though the three-dimensional structures of barley alpha-amylase isozymes AMY1 and AMY2 are very similar, they differ remarkably from each other in their affinity for Ca(2+) and when interacting with substrate analogs. A surface site recognizing maltooligosaccharides, not earlier reported for other alpha-amylases and probably associated with the different activity of AMY1 and AMY2 toward starch granules, has been identified. It is located in the C-terminal part of the enzyme and, thus, highlights a potential role of domain C. In order to scrutinize the possible biological significance of this domain in alpha-amylases, a thorough comparison of their three-dimensional structures was conducted. An additional role for an earlier-identified starch granule binding surface site is proposed, and a new calcium ion is reported.
Robert
Xavier
X
Laboratoire de BioCristallographie, Institut de Biologie et Chimie des Protéines, UMR 5086-CNRS/UCBL1, 7 Passage du Vercors, F-69367 Lyon cedex 07, France.
Haser
Richard
R
Gottschalk
Tine E
TE
Ratajczak
Fabien
F
Driguez
Hugues
H
Svensson
Birte
B
Aghajari
Nushin
N
D020909:Acarbose / Q000737:chemistry; D000595:Amino Acid Sequence; D002118:Calcium / Q000737:chemistry / Q000378:metabolism; D050260:Carbohydrate Metabolism; D002241:Carbohydrates / Q000737:chemistry*; D002384:Catalysis; D018360:Crystallography, X-Ray; D001467:Hordeum / Q000201:enzymology*; D006860:Hydrogen Bonding; D057927:Hydrophobic and Hydrophilic Interactions; D007527:Isoenzymes / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008024:Ligands; D008958:Models, Molecular; D008969:Molecular Sequence Data; D015394:Molecular Structure; D010843:Pichia / Q000201:enzymology; D011485:Protein Binding; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary / Q000502:physiology*; D017386:Sequence Homology, Amino Acid; D013213:Starch / Q000737:chemistry / Q000378:metabolism; D013379:Substrate Specificity; D014443:Tyrosine / Q000737:chemistry / Q000378:metabolism; D014867:Water / Q000737:chemistry; D000516:alpha-Amylases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
D002241:Carbohydrates; D007527:Isoenzymes; D008024:Ligands; D014867:Water; D014443:Tyrosine; D013213:Starch; D000516:alpha-Amylases; D002118:Calcium; D020909:Acarbose