The Role of Co2+ in the Crystallization of Human Senp1 and Comments on the Limitations of Automated Refinement Protocols
Rimsa, V., Eadsforth, T., Hay, R.T., Hunter, W.N.(2011) Acta Crystallogr Sect F Struct Biol Cryst Commun 67: 442
- PubMed: 21505236 
- DOI: https://doi.org/10.1107/S1744309111005835
- Primary Citation of Related Structures:  
2XPH, 2XRE - PubMed Abstract: 
Metal ions often stabilize intermolecular contacts between macromolecules, thereby promoting crystallization. When interpreting a medium-resolution electron-density map of the catalytic domain of human sentrin-specific protease 1 (SENP1), a strong feature indicative of an ordered divalent cation was noted. This was assigned as Co(2+), an essential component of the crystallization mixture. The ion displays tetrahedral coordination by Glu430 and His640 from one molecule and the corresponding residues from a symmetry-related molecule. Analysis of the data derived from a previous structure of SENP1 suggested that Co(2+) had been overlooked and re-refinement supported this conclusion. High-throughput automated re-refinement protocols also failed to mark the Co(2+) position, supporting the requirement for the incorporation of as much information as possible to enhance the value of such protocols.
Organizational Affiliation: 
Division of Biological Chemistry and Drug Discovery, College of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland.