A conserved Glu-Arg salt bridge connects coevolved motifs that define the eukaryotic protein kinase fold.
Yang, J., Wu, J., Steichen, J.M., Kornev, A.P., Deal, M.S., Li, S., Sankaran, B., Woods, V.L., Taylor, S.S.(2012) J Mol Biol 415: 666-679
- PubMed: 22138346 
- DOI: 10.1016/j.jmb.2011.11.035
- Primary Citation of Related Structures:  
3QAL, 3QAM - PubMed Abstract: 
Eukaryotic protein kinases (EPKs) feature two coevolved structural segments, the Activation segment, which starts with the Asp-Phe-Gly (DFG) and ends with the Ala-Pro-Glu (APE) motifs, and the helical GHI subdomain that comprises αG-αH-αI helices. Eukaryotic-like kinases have a much shorter Activation segment and lack the GHI subdomain ...