1. X-ray-Radiation-Induced Changes in Bacteriorhodopsin Structure
- Author
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Borshchevskiy, Valentin I., Round, Ekaterina S., Popov, Alexandr N., Büldt, Georg, and Gordeliy, Valentin I.
- Subjects
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X-rays , *ABSORPTION , *BACTERIORHODOPSIN , *PROTON transfer reactions , *CELL membranes , *SCHIFF bases , *MEMBRANE proteins , *RADIATION injuries , *X-ray crystallography - Abstract
Abstract: Bacteriorhodopsin (bR) provides light-driven vectorial proton transport across a cell membrane. Creation of electrochemical potential at the membrane is a universal step in energy transformation in a cell. Published atomic crystallographic models of early intermediate states of bR show a significant difference between them, and conclusions about pumping mechanisms have been contradictory. Here, we present a quantitative high-resolution crystallographic study of conformational changes in bR induced by X-ray absorption. It is shown that X-ray doses that are usually accumulated during data collection for intermediate-state studies are sufficient to significantly alter the structure of the protein. X-ray-induced changes occur primarily in the active site of bR. Structural modeling showed that X-ray absorption triggers retinal isomerization accompanied by the disappearance of electron densities corresponding to the water molecule W402 bound to the Schiff base. It is demonstrated that these and other X-ray-induced changes may mimic functional conformational changes of bR leading to misinterpretation of the earlier obtained X-ray crystallographic structures of photointermediates. [Copyright &y& Elsevier]
- Published
- 2011
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