Linked Life Data

18453695

Source:http://linkedlifedata.com/resource/pubmed/id/18453695

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
Pt 5
pubmed:dateCreated
2008-5-5
pubmed:abstractText
The crystal structure of cytokinin-specific binding protein (CSBP) containing four independent molecules with 4 x 155 = 620 residues in the asymmetric unit of the P6(4) unit cell has been solved by three-wavelength MAD using 1.8 angstroms resolution data recorded from a crystal derivatized with the dodecabromohexatantalum cation (Ta6Br12)2+. The diffraction data contained a very strong anomalous signal (allowing successful phasing even using peak SAD data alone) despite the fact that the five (Ta6Br12)2+ clusters found in the asymmetric unit have low occupancy (about 0.3). The derivative structure has been successfully refined to R = 0.158, providing interesting details on the geometry of the (Ta6Br12)2+ cluster, its interactions with the protein and on the backsoaking of a cytokinin ligand that was originally part of a CSBP-cytokinin complex in the native crystals used for (Ta6Br12)2+ derivatization. A simulation analysis of the phasing power of the (Ta6Br12)2+ ions at artificially imposed resolution limits shows that it is not possible to resolve the individual Ta atoms if the dmin limit of the data is higher than 2.9 angstroms. Additionally, for successful Ta identification the (Ta6Br12)2+ complex should be specifically bound and ordered. Good binding at the protein surface is facilitated by the presence of acidic groups, indicating higher pH buffer conditions to be preferable. In addition, the water channels in the crystal should be sufficiently wide (at least 11 angstroms) to allow free diffusion of the (Ta6Br12)2+ ions on soaking. A retrospective look at the initial molecular-replacement calculations provides interesting insights into how the peculiar packing mode and strong bias of the molecular-replacement-phased electron-density maps had hindered successful solution of the structure by this method.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
May
pubmed:issn
0907-4449
pubmed:author
pubmed:issnType
Print
pubmed:volume
64
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
595-606
pubmed:dateRevised
2011-11-17
pubmed:meshHeading
pubmed:year
2008
pubmed:articleTitle
MAD phasing using the (Ta6Br12)2+ cluster: a retrospective study.
pubmed:affiliation
Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Poland.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't