Radiation-induced site-specific damage of mercury derivatives: phasing and implications.
- Resource Type
- Article
- Authors
- Ramagopal, Udupi A.; Dauter, Zbigniew; Thirumuruhan, Radhakannan; Fedorov, Elena; Almo, Steven C.
- Source
- Acta Crystallographica: Section D (Wiley-Blackwell). Sep2005, Vol. 61 Issue 9, p1289-1298. 10p.
- Subject
- *IRRADIATION
*RADIATION
*X-rays
*ELECTRON distribution
*ELECTRONS
*CRYSTALLOGRAPHY
*PARTICLES (Nuclear physics)
- Language
- ISSN
- 0907-4449
The behavior of mercury-derivatized triclinic crystals of a 60 kDa protein target from the New York Structural GenomiX Research Consortium provides novel insights into the mechanism of heavy-atom-specific radiation damage and its potential exploitation for de novo structure solution. Despite significant anomalous signal, structure solution by classic SAD and MAD phasing approaches was not successful. A detailed analysis revealed that significant isomorphic variation of the diffracted intensities was induced by X-ray irradiation. These intensity changes allowed the crystal structure to be solved by the radiation-damage-induced phasing (RIP) technique. Inspection of the crystal structure and electron-density maps demonstrated that the covalent S-Hg bonds at all four derivatized cysteine sites were much more susceptible to radiation-induced cleavage than other bonds typically present in native proteins. A simple diagnostic is described to identify the fingerprint of such decay at the time of data collection/processing. The rapid radiation-induced decomposition of mercury adducts is consistent with the difficulties frequently associated with the experimental phasing of mercury derivatives and suggests a straightforward solution to overcome this limitation by radiation-damage-induced phasing with anomalous scattering (RIPAS). These results indicate that historically recalcitrant and newly emerging difficulties associated with Hg phasing should be revisited. [ABSTRACT FROM AUTHOR]