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== Structural highlights == | == Structural highlights == | ||
Shown as 1hvx is the structure of the thermostable α-amylase of Bacillus stearothermophilus (BSTA)[3]. BSTA is comprised of a single polypeptide chain. This chain is folded into three domains: A, B and C. These domains are generally found on all α-amylase enzymes. The <scene name='60/609816/A_domain/1'>A domain</scene> constitutes the core structure, with a (β/α)8-barrel.The <scene name='60/609816/B_domain/1'>B domain</scene> consists of a sheet of four anti-parallel β-strands with a pair of anti-parallel β-strands. Long loops are observed between the β-strands. Located within the B domain is the binding site for Ca2+-Na+-Ca2+.<scene name='60/609816/Domain_c/1'>Domain C</scene> consisting of eight β-strands is assembled into a globular unit forming a Greek key motif. It also holds the third Ca2+ binding site in association with domain A. Positioned on the C-terminal side of the β-strands of the (β/α)8-barrel in domain A is the active site. The catalytic residues involved for the BSTA active site are<scene name='60/609816/Aga/1'> Asp234, Glu264, and Asp331</scene> | Shown as 1hvx is the structure of the thermostable α-amylase of Bacillus stearothermophilus (BSTA)[3]. BSTA is comprised of a single polypeptide chain. This chain is folded into three domains: A, B and C. These domains are generally found on all α-amylase enzymes. The <scene name='60/609816/A_domain/1'>A domain</scene> constitutes the core structure, with a (β/α)8-barrel.The <scene name='60/609816/B_domain/1'>B domain</scene> consists of a sheet of four anti-parallel β-strands with a pair of anti-parallel β-strands. Long loops are observed between the β-strands. Located within the B domain is the binding site for Ca2+-Na+-Ca2+.<scene name='60/609816/Domain_c/1'>Domain C</scene> consisting of eight β-strands is assembled into a globular unit forming a Greek key motif. It also holds the third Ca2+ binding site in association with domain A. Positioned on the C-terminal side of the β-strands of the (β/α)8-barrel in domain A is the active site. The catalytic residues involved for the BSTA active site are<scene name='60/609816/Aga/1'> Asp234, Glu264, and Asp331</scene>.The residues are identical to other α-amylases, yet there are positional differences which reflect the flexible nature of catalytic resides. CaII and CaI with Na found in the interior of domain B and CaIII at the interface of domain A and C, constitute the metal ion binding sites. All α-amylases contain one strongly conserved Ca2+ ion for structural integrity and enzymatic activity.[4] CaI is consistent in α-amylases, however there are structural differences between the linear trio of CaI, CaII and Na in other enzymes. CaIII acts as a bridge between two loops, one from α6 of domain A, and one between β1 and β2 of domain C. | ||
</StructureSection> | </StructureSection> | ||