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From:
doi: 10.1128/MMBR.70.1.157-176.2006

FIG. 2.

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Topology diagrams of members of α-amylase family GH13 (A) and GS proteins of family GH70 (B). The catalytic domain of α-amylases has a (β/α)8 barrel structure, starting with β-strand 1 and ending with α-helix 8. The B domain is located between β-strand 3 and α-helix 3. GS have a putative circularly permuted (β/α)8 barrel structure (111), which starts with α-helix 3 (α-amylase numbering) and ends with β-strand 3. Between α-helix 8 and β-strand 1, a large stretch of unknown function is located. The locations of the four conserved regions (I to IV) in family GH13 (and family GH70) are indicated with dashed boxes. Amylosucrase has a domain loop (B′ domain; important for polymerizing activity; indicated with a dashed line and circle) consisting of approximately 60 amino acid residues which is located after β-strand 7 (182, 183), immediately after the two catalytically important His392 and Asp393 residues located in conserved region IV (165) (Fig. (Fig.1).1). GS proteins also contain an additional “loop” (about 45 amino acids; indicated with a dashed line) compared to α-amylase enzymes, which is located between β-strand 7 and α-helix 7. Conceivably, this loop is also important for polymerizing activity. The approximate sites of the three catalytic residues (D, E, and D) are indicated. B, B domain; C, C domain; GBD, glucan binding domain; VR, variable region. (Adapted from reference 96 with permission of the publisher. Copyright 2005 American Chemical Society.)

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