Solution of the structure of Aspergillus niger acid alpha-amylase by combined molecular replacement and multiple isomorphous replacement methods.
The crystal structure of Aspergillus niger acid alpha-amylase was solved by a combination of multiple isomorphous replacement and molecular replacement methods. The atomic coordinates of Aspergillus oryzae (TAKA) alpha-amylase (entry 2TAA in the Protein Data Bank) and experimental diffraction data from a new monoclinic crystal form of TAKA alpha-amylase, were used during the procedure. Sequence identity between the two proteins is approximately 80%. The atomic parameters derived from the molecular replacement solution were too inaccurate to initiate least-squares crystallographic refinement. The molecular model was extensively revised against the experimental electron density map calculated at 3 A resolution. Subsequent crystallographic refinement of this model using synchrotron data to 2.1 A resolution led to a conventional R factor of 16.8%. The structure conforms well to expected stereochemistry with bond lengths deviating from target values by 0.031 A, and planar groups showing a root-mean-square deviation from ideal planes of 0.025 A.
Department of Chemistry, University of York, Heslington, England.
R L
RL
Brady
A M
AM
Brzozowski
Z S
ZS
Derewenda
E J
EJ
Dodson
G G
GG
Dodson
D001234:Aspergillus niger / Q000201:enzymology*; D001236:Aspergillus oryzae / Q000201:enzymology; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003460:Crystallization; D015394:Molecular Structure; D014961:X-Ray Diffraction; D000516:alpha-Amylases / Q000737:chemistry*
D000516:alpha-Amylases