Structure of Raw Starch-Digesting Bacillus cereus -Amylase Complexed with Maltose
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- 作者：Bunzo Mikami ; Motoyasu Adachi ; Takihiro Kage ; Elif Sarikaya ; Takashi Nanmori ; Ryu Shinke ; and Shigeru Utsumi
- 刊名：Biochemistry
- 出版年：1999
- 出版时间：June 1, 1999
- 年：1999
- 卷：38
- 期：22
- 页码：7050 - 7061
- 全文大小：285K
- 年卷期：v.38,no.22(June 1, 1999)
- ISSN：1520-4995
文摘
The crystals of 
-amylase from Bacillus cereus belong to space group P21 with the followingcell dimensions: a = 57.70 Å, b = 92.87 Å, c = 65.93 Å, and =101.95
. The structures of free andmaltose-bound -amylases were determined by X-ray crystallography at 2.1 and 2.5 Å with R-factors of0.170 and 0.164, respectively. The final model of the maltose-bound form comprises 516 amino acidresidues, four maltose molecules, 275 water molecules, one Ca2+, one acetate, and one sulfate ion. Theenzyme consists of a core (/
)8-barrel domain (residues 5-434) and a C-terminal starch-binding domain(residues 435-613). Besides the active site in the core where two maltose molecules are bound in tandem,two novel maltose-binding sites were found in the core L4 region and in the C-terminal domain. Thestructure of the core domain is similar to that of soybean -amylase except for the L4 maltose-bindingsite, whereas the C-terminal domain has the same secondary structure as domain E of cyclodextringlucosyltransferase. These two maltose-binding sites are 32-36 Å apart from the active site. These resultsindicate that the ability of B. cereus -amylase to digest raw starch can be attributed to the additional twomaltose-binding sites.
-amylase from Bacillus cereus belong to space group P21 with the followingcell dimensions: a = 57.70 Å, b = 92.87 Å, c = 65.93 Å, and =101.95. The structures of free andmaltose-bound -amylases were determined by X-ray crystallography at 2.1 and 2.5 Å with R-factors of0.170 and 0.164, respectively. The final model of the maltose-bound form comprises 516 amino acidresidues, four maltose molecules, 275 water molecules, one Ca2+, one acetate, and one sulfate ion. Theenzyme consists of a core (/)8-barrel domain (residues 5-434) and a C-terminal starch-binding domain(residues 435-613). Besides the active site in the core where two maltose molecules are bound in tandem,two novel maltose-binding sites were found in the core L4 region and in the C-terminal domain. Thestructure of the core domain is similar to that of soybean -amylase except for the L4 maltose-bindingsite, whereas the C-terminal domain has the same secondary structure as domain E of cyclodextringlucosyltransferase. These two maltose-binding sites are 32-36 Å apart from the active site. These resultsindicate that the ability of B. cereus -amylase to digest raw starch can be attributed to the additional twomaltose-binding sites.