Low-resolution structural characterization of the arginine repressor/activator from Bacillus subtilis: a combined X-ray crystallographic and electron microscopical approach.
Attempts to determine the X-ray crystal structure of the intact homohexameric arginine repressor/activator from B. subtilis have so far been unsuccessful. The major problem appears to be the lack of an isomorphous heavy-atom derivative with a manageable number of substitution sites. Here it is shown how electron microscopy of thin three-dimensional crystals, the same as those used for the X-ray crystallographic studies, made it possible (i) to obtain experimental support for some conclusions drawn on the basis of X-ray data alone, (ii) to determine the low-resolution distribution of electron density in several different crystallographic projections, and (iii) to obtain a tentative low-resolution model of the whole hexamer.
Department of Biochemistry and Molecular Biology, University of Leeds, Leeds LS2 9JT, England.
N M
NM
Glykos
A
A
Holzenburg
S E
SE
Phillips
D001412:Bacillus subtilis / Q000737:chemistry; D001426:Bacterial Proteins / Q000737:chemistry* / Q000648:ultrastructure*; D018360:Crystallography, X-Ray / Q000379:methods*; D003627:Data Interpretation, Statistical; D007091:Image Processing, Computer-Assisted; D008854:Microscopy, Electron / Q000379:methods*; D008958:Models, Molecular; D011487:Protein Conformation; D012097:Repressor Proteins / Q000737:chemistry* / Q000648:ultrastructure*
C087018:ArgR protein, Bacteria; D001426:Bacterial Proteins; D012097:Repressor Proteins