1G94

CRYSTAL STRUCTURE ANALYSIS OF THE TERNARY COMPLEX BETWEEN PSYCHROPHILIC ALPHA AMYLASE FROM PSEUDOALTEROMONAS HALOPLANCTIS IN COMPLEX WITH A HEPTA-SACCHARIDE AND A TRIS MOLECULE

Summary for 1G94

• Entry DOI: 10.2210/pdb1g94/pdb
• Related: 1AQH 1AQM 1b0i
• Descriptor: ALPHA-AMYLASE, 4,6-dideoxy-4-{[(1S,5R,6S)-3-formyl-5,6-dihydroxy-4-oxocyclohex-2-en-1-yl]amino}-alpha-D-xylo-hex-5-enopyranose-(1-4)-alpha-D-glucopyranose, 4,6-dideoxy-4-{[(1S,5R,6S)-3-formyl-5,6-dihydroxy-4-oxocyclohex-2-en-1-yl]amino}-alpha-D-xylo-hex-5-enopyranose-(1-4)-alpha-D-glucopyranose-(1-4)-alpha-D-glucopyranose, ... (7 entities in total)
• Functional Keywords: beta-alpha-8-barrel, 3 domain structure, hydrolase
• Biological source: Pseudoalteromonas haloplanktis
• Cellular location: Secreted : P29957
• Total number of polymer chains: 1
• Total formula weight: 50262.07

Authors

Aghajari, N.,Roth, M.,Haser, R. (deposition date: 2000-11-22, release date: 2001-12-12, Last modification date: 2023-08-09)

Primary citation

Aghajari, N.,Roth, M.,Haser, R.
Crystallographic evidence of a transglycosylation reaction: ternary complexes of a psychrophilic alpha-amylase.
Biochemistry, 41:4273-4280, 2002

PubMed Abstract: The psychrophilic Pseudoalteromonas haloplanctis alpha-amylase is shown to form ternary complexes with two alpha-amylase inhibitors present in the active site region, namely, a molecule of Tris and a trisaccharide inhibitor or heptasaccharide inhibitor, respectively. The crystal structures of these complexes have been determined by X-ray crystallography to 1.80 and 1.74 A resolution, respectively. In both cases, the prebound inhibitor Tris is expelled from the active site by the incoming oligosaccharide inhibitor substrate analogue, but stays linked to it, forming well-defined ternary complexes with the enzyme. These results illustrate competition in the crystalline state between two inhibitors, an oligosaccharide substrate analogue and a Tris molecule, bound at the same time in the active site region. Taken together, these structures show that the enzyme performs transglycosylation in the complex with the pseudotetrasaccharide acarbose (confirmed by a mutant structure), leading to a well-defined heptasaccharide, considered as a more potent inhibitor. Furthermore, the substrate-induced ordering of water molecules within a channel highlights a possible pathway used for hydrolysis of starch and related poly- and oligosaccharides.

PubMed: 11914073
DOI: 10.1021/bi0160516

Experimental method

X-RAY DIFFRACTION (1.74 Å)