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Titolo:
CRYSTAL-STRUCTURE OF THERMOSTABLE ALPHA-AMYLASE FROM BACILLUS-LICHENIFORMIS REFINED AT 1.7 ANGSTROM RESOLUTION
Autore:
HWANG KY; SONG HK; CHANG C; LEE J; LEE SY; KIM KK; CHOE S; SWEET RM; SUH SW;
Indirizzi:
SEOUL NATL UNIV,DEPT CHEM SEOUL 151742 SOUTH KOREA SEOUL NATL UNIV,DEPT CHEM SEOUL 151742 SOUTH KOREA SEOUL NATL UNIV,CTR MOL CATALYSIS SEOUL 151742 SOUTH KOREA SALK INST BIOL STUDIES,STRUCT BIOL LAB LA JOLLA CA 92037 BROOKHAVEN NATL LAB,DEPT BIOL UPTON NY 11973
Titolo Testata:
Molecules and cells
fascicolo: 2, volume: 7, anno: 1997,
pagine: 251 - 258
SICI:
1016-8478(1997)7:2<251:COTAFB>2.0.ZU;2-#
Fonte:
ISI
Lingua:
ENG
Soggetto:
X-RAY-DIFFRACTION; MOLECULAR-MODEL REFINEMENT; AMINO-ACID SEQUENCES; MACROMOLECULAR CRYSTALLOGRAPHY; WEISSENBERG CAMERA; ASPERGILLUS; CALCIUM; CRYSTALLIZATION; PROTEINS; DETECTOR;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
38
Recensione:
Indirizzi per estratti:
Citazione:
K.Y. Hwang et al., "CRYSTAL-STRUCTURE OF THERMOSTABLE ALPHA-AMYLASE FROM BACILLUS-LICHENIFORMIS REFINED AT 1.7 ANGSTROM RESOLUTION", Molecules and cells, 7(2), 1997, pp. 251-258

Abstract

alpha-Amylases (alpha-1,4-glucan-4-glucanohydrolase, E.C.3.2.1.1) catalyze the cleavage of alpha-1, 4-glucosidic linkages of starch components, glycogen, and various oligosaccharides. Thermostable alpha-amylases from Bacillus species are of great industrial importance in the production of corn syrup or dextrose. Thermostable alpha-amylase from Bacillus licheniformis, a monomeric enzyme with molecular mass of 55,200 Da (483 amino acid residues), shows a remarkable heat stability. This enzyme provides an attractive model for investigating the structural basis for thermostability of proteins. The three-dimensional structure of thermostable alpha-amylase from Bacillus licheniformis has been determined by the multiple isomorphous replacement method of X-ray crystallography. The structure has been refined to a crystallographic R-factor of 19.9% for 58,601 independent reflections with F-o>2 sigma Fo between 8.0 and 1.7 Angstrom resolution, with root mean square deviationsof 0.013 Angstrom from ideal bond lengths and 1.72 degrees from idealbond angles. The final model consists of 469 amino acid residues and 294 water molecules, Missing from the model are the N- and C-termini and the segment between Trp182 and Asn192. Like other alpha-amylases, the polypeptide chain folds into three distinct domains. The first domain (domain A), consisting of 291 residues (from residue 3 to 103 and 207 to 396), forms a (beta/alpha)(s)-barrel structure. The second domain (domain B), consisting of residues 104 to 206, is inserted between the third beta-strand and the third alpha-helix of domain A. The third C-terminal domain (domain C), consisting of residues 397 to 482, foldsinto an eight-stranded antiparallel beta-barrel. Neither calcium ion nor chloride ion is located near the active site. This study reveals the architecture of the thermostable alpha-amylase from Bacillus licheniformis. By homology with other alpha-amylases, important active site residues can be identified as Asp231, Glu261, and Asp328, which are all located at the C-terminal end of the central (beta/alpha)(s)-barrel. Since many of the stabilizing and destabilizing mutations obtained sofar fall in domain B or at its border, this region of the enzyme appears to be important for thermostability. The factors responsible for the remarkable thermostability of this enzyme may be increased ionic interactions, reduced surface area, and increased packing interactions in the interior.

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Documento generato il 11/07/20 alle ore 04:11:01