A1 Refereed original research article in a scientific journal
Structure determination by multiwavelength anomalous diffraction of aclacinomycin oxidoreductase: indications of multidomain pseudomerohedral twinning
Authors: Sultana A, Alexeev I, Kursula I, Mantsala P, Niemi J, Schneider G
Publisher: BLACKWELL PUBLISHING
Publication year: 2007
Journal:Acta Crystallographica Section D: Biological Crystallography
Journal name in sourceACTA CRYSTALLOGRAPHICA SECTION D-BIOLOGICAL CRYSTALLOGRAPHY
Journal acronym: ACTA CRYSTALLOGR D
Volume: 63
First page : 149
Last page: 159
Number of pages: 11
ISSN: 0907-4449
DOI: https://doi.org/10.1107/S0907444906044271
Abstract
The crystal structure of aclacinomycin oxidoreductase (AknOx), a tailoring enzyme involved in the biosynthesis of the polyketide antibiotic aclacinomycin, was determined to 1.65 A resolution by multiwavelength anomalous diffraction using data from selenomethionine- substituted crystals. The crystals belong to space group P2(1), with unit-cell parameters a = 68.2, b = 264.5, c = 68.2 angstrom, beta = 119 degrees. Analysis of the intensity statistics clearly showed the presence of pseudomerohedral twinning. The data set could also be indexed and scaled with an R-sym of 0.072 in the orthorhombic space group C222(1) (unit-cell parameters a = 69.7, b = 117.5, c = 264.4 angstrom), indicating the possibility of pseudomerohedral twinning along the diagonal between the monoclinic a and c directions. Refinement using this twin operator resulted in an R-free of 24.2%. A monoclinic lattice with a = c and beta close to 120 degrees can emulate a hexagonal metric, with the possibility of a threefold twin operator along the b axis and three twin domains. Refinement assuming three-domain twinning gave a final Rfree of 26.5%. The structure of AknOx can be thus refined with comparable Rfree values using either of the twin operators separately, suggesting the possibility that crystals of AknOx contain six twin domains generated by the twofold and threefold twin operators perpendicular to each other. Both twin operators coincide with noncrystallographic symmetry axes that may promote twinning.
The crystal structure of aclacinomycin oxidoreductase (AknOx), a tailoring enzyme involved in the biosynthesis of the polyketide antibiotic aclacinomycin, was determined to 1.65 A resolution by multiwavelength anomalous diffraction using data from selenomethionine- substituted crystals. The crystals belong to space group P2(1), with unit-cell parameters a = 68.2, b = 264.5, c = 68.2 angstrom, beta = 119 degrees. Analysis of the intensity statistics clearly showed the presence of pseudomerohedral twinning. The data set could also be indexed and scaled with an R-sym of 0.072 in the orthorhombic space group C222(1) (unit-cell parameters a = 69.7, b = 117.5, c = 264.4 angstrom), indicating the possibility of pseudomerohedral twinning along the diagonal between the monoclinic a and c directions. Refinement using this twin operator resulted in an R-free of 24.2%. A monoclinic lattice with a = c and beta close to 120 degrees can emulate a hexagonal metric, with the possibility of a threefold twin operator along the b axis and three twin domains. Refinement assuming three-domain twinning gave a final Rfree of 26.5%. The structure of AknOx can be thus refined with comparable Rfree values using either of the twin operators separately, suggesting the possibility that crystals of AknOx contain six twin domains generated by the twofold and threefold twin operators perpendicular to each other. Both twin operators coincide with noncrystallographic symmetry axes that may promote twinning.
UTU Research Portal