Our lab is trying to crystallize a highly soluble (100+ mg/ml) protein with a molecular weight of 35 kd.
The protein was screened against 1536 conditions at 20 mg/mL. Most drops were either clear or produced "bubbles" (often oily looking). The few that had precipitate contained high concentrations of K3PO4, cobalt, or zinc. We have tried repeating some of the bubble conditions at 100+ mg/mL and are still getting clear drops or bubbles. Is there something about highly soluble proteins and/or secreted proteins and/or proteins with unusual portions of their sequence that needs to be considered in order to successfully crystallize it? I am considering trying "salting out" using dialysis, and also adding ligands/inhibitors. The protein is in 50 mM NaCl plus 50 mM buffer. I welcome thoughts and suggestions on crystallization ideas, publications, etc. Thank you Yvonne
