The structure of rabbit muscle glycogen phosphorylase b, an important regulatory enzyme in glycogen metabolism, has been studied by X-ray crystallographic techniques. This work was carried out as part of a group project, and the crystal structure of the enzyme had already been solved to 3 Å resolution, using the technique of Multiple Isomorphous Replacement. A search for additional heavy atom isomorphous derivatives was carried out, and photographic data to 3 Å resolution were collected for a further ethylmercurythiosalicylate derivative, using a screenless oscillation camera. The collection and reduction of this data, and the refinement of the heavy atom positions is described. The inclusion of this data allowed a new electron density map (with figure of merit = O.63) to be calculated, which enabled previously ambiguous areas in the electron density to be interpreted. Data to 2 Å resolution have been collected on an oscillation camera, using a synchrotron radiation source and cylindrical film cassettes. An intensity gain of up to 13O times, compared to a GX6 rotating anode source, was obtained with the synchrotron radiation source. A reduction in radiation damage, was also observed. The collection and reduction of the 2 Å data is described. The final overall merging R-factor was 15%. Some systematic errors remain in the data, and possible sources of these errors are discussed, and improvements to the data processing procedure suggested. The 2 Å data were empirically scaled to the 3 Å data and have been used in the first stages of the refinement of the phosphorylase b structure. The contribution of the crystallographic results towards an understanding of phosphorylase b as an allosteric protein is discussed.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:580772 |
| Date | January 1981 |
| Creators | Wild, David Leslie |
| Contributors | Wilson, Keith |
| Publisher | University of Oxford |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://ora.ox.ac.uk/objects/uuid:9fc21eb2-0f97-4925-8993-a82937f74dbb |
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