Open AccessPurification, crystallization and preliminary X‐ray analysis of an acetylxylan esterase from Bacillus pumilus . Erratum
Author(s) -
Benini Stefano,
Degrassi Giuliano,
Krastanova Ivet,
Lamba Doriano,
Venturi Vittorio
Publication year - 2004
Publication title -
acta crystallographica section d
Language(s) - English
Resource type - Journals
ISSN - 1399-0047
DOI - 10.1107/s0907444904014040
Subject(s) - bacillus pumilus , crystallization , escherichia coli , bacillus subtilis , protein data bank (rcsb pdb) , crystallography , chemistry , esterase , molecular replacement , biochemistry , biology , enzyme , bacteria , organic chemistry , genetics , gene
This erratum is to apologise for having reported the crystallization and X‐ray characterization of Bacillus pumilus acetylxylan esterase (AXE) while the protein crystallized was instead an inorganic pyrophosphatase, a contaminant of the expression in E. coli . The protein was purified by hydrophobic interaction, ionic exchange and gel filtration, but still contained traces of contaminant proteins. Crystals were obtained in the R 32 space group perfectly compatible with the homohexameric structure of AXE. The cell parameters were compatible with a reasonable crystal packing as in the model cephalosporin C deacetylase from Bacillus subtilis kindly provided before publication by Dr Jim Brannigan et al . (PDB code 1ods crystallized in R 3 and 1odt crystallized in R 32). Since every attempt to solve the structure by molecular replacement using 1odt as a model failed, a search of the PDB using the cell parameters of the data collected revealed a match with Escherichia coli inorganic pyrophosphatase ( 1ipw ). A molecular‐replacement solution confirmed that the protein crystallized was indeed E. coli inorganic pyrophosphatase present as a contaminant in the protein preparation used for crystallization. This experience should be kept in mind because proteins used for crystallization should be as pure as possible not only to favour the process itself but also to avoid the crystallization of contaminants.