Hi everyone,
Can Arginine inhibit the crystallization process of a protein? I use 500mM Arginine to suppress the aggregation of my protein (30mM HEPES,pH7.5; 150mM NaCl; 5% Glycerol; 500mM Arginine, 5mM BME). I have screened many crystal conditions to get the crystals. However, i have not got any crystals, therefore i was wondering if Arginine could inhibit the crystallization process.
Kindly share your experience in this.
Thanks & Regards
Sunil Singh
Hi Sunil,
Arg improves protein solubility, but i doubt it is your major problem in protein crystallization. With some proteins I had no crystals in spite of thousand of different conditions tested. Anyway, you could try to cut the Arg concentration to 100mM (if your protein is still stable) or to minimum Arg requested to keep it soluble.
I doubt it's a problem. In any case check for Arg concentrations in crystalisation conditions in the PDB
Hi Sunil,
I've started using L-Arginine to avoid protein aggregation and I'm still struggling to get crystals. I agree with Emmanuele, that you should try lowering the Arg concentration. Because I recently decreased the L-Arg concentration from 100 mM to 25 mM and also lowered the NaCl concentration and started observing some crystalline needles. I've found a paper which suggests that amino acids and amino acid derivatives generally promote protein crystallization. Please read here: http://journals.iucr.org/s/issues/2008/03/00/ys5038/index.html
I would try lowering not only the arginine concentration (to lower than 100mM) but as well NaCl (maybe not more than 50mM?) if it is possible , then a crystallization condition would have stronger effect on your protein
Dear All,
Thank you so much for your insightful suggestions.
Regards,
Sunil Singh
Indeed, it's helping to keep the protein in solution, which is the opposite of what you want to achieve when crystallizing.
You can lower the arginine to 100 or 50 mM and see. You can eventually also add glutamate. I actually had a 50mM Arg + 50mM Glu mixture in mind as a solution to help keeping proteins soluble.
As another try, I would try (much) higher protein concentration, in order to reach the nucleation zone.
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