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Hi, a likely scenario is that your mutant crystallises in the same conformation/packing as the wild-type protein, and this conformation is good for ligand binding. In solution, your mutant protein may be more flexible/open than the wild-type and affinity hence lower. We see this quite often. Various solution structure techniques will shed light on this. Another possibility, assuming that you did ITC only at one temperature, is that you are “lucky” enough to be at the temperature where enthalpy for binding is zero for the mutant (but not wild-type). This you can find out by carrying out ITC at different temperatures. Petri Petri Kursula ---------- Professor ---------- Department of Biomedicine University of Bergen, Norway http://www.uib.no/en/rg/petrikursula [log in to unmask] ---------- Faculty of Biochemistry and Molecular Medicine Biocenter Oulu University of Oulu, Finland ---------- > On 22 Feb 2020, at 07:31, monika chandravanshi <[log in to unmask]> wrote: > > Dear All, > > I have a situation, where a mutant protein does not exhibit any heat change upon titration with cognate ligand in the ITC experiment. However, it co-crystallizes with the respective cognate ligand. Also, the cocrystal structure reveals the conservation of the hydrogen bonding networks except for the mutated residues. I would like to know the possible reason for the no heat change in the ITC experiment. > > Looking forward to hearing from you. > > -- > ----- > > With Kind Regards > > Monika Chandravanshi > PhD Scholar, > Department of Biosciences and Bioengineering > Indian Institute of Technology Guwahati, Guwahati India > > To unsubscribe from the CCP4BB list, click the following link: > https://www.jiscmail.ac.uk/cgi-bin/webadmin?SUBED1=CCP4BB&A=1 <https://www.jiscmail.ac.uk/cgi-bin/webadmin?SUBED1=CCP4BB&A=1> ######################################################################## To unsubscribe from the CCP4BB list, click the following link: https://www.jiscmail.ac.uk/cgi-bin/webadmin?SUBED1=CCP4BB&A=1