Hi Todd, A concern of mine is that you may be looking at an artifact of the domain. Whatever assays you decide to do, make sure that they are also performed for the full sized protein.
Best wishes, Reza Reza Khayat, PhD Assistant Professor The City College of New York Department of Chemistry, MR-1135 160 Convent Avenue New York, NY 10031 Tel. (212) 650-6070 www.khayatlab.org ---- Original message ---- >Date: Sat, 20 Dec 2014 10:44:25 -0800 >From: CCP4 bulletin board <[email protected]> (on behalf of Christine Gee <[email protected]>) >Subject: Re: [ccp4bb] non-specific disulfide bonds in crystal structures >To: [email protected] > > Hi Todd, > I used to work on PNMT which also is supposedly > monomeric and formed a disulfide between monomers in > the crystals. > See http://www.sciencedirect.com/science/article/pii/S157096390 5000968?via=ihub > We showed that it was irrelevant to activity. > Cheers > Christine > Sent from my iPad > On 20 Dec 2014, at 9:52 am, Todd Jason Green > <[email protected]> wrote: > > Hello All- > > I have recently determined a domain structure of a > larger protein. The structure shows a clear > disulfide bond between two monomers in the > asymmetric unit. I'm trying to figure out if this > is an artifact of the crystal packing or has > biological relevance. The protein has been > reported to function as a monomer. If I look at > the pool of protein on a SDS-PAGE gel under > non-reducing conditions, I see that a smaller > percentage (~15-20%) of the protein runs as a > dimer. In the structure, the association has > 2-fold symmetry with about 29% of the monomeric > surface area buried between the dimer. Can anyone > point me in the direction of a paper describing a > non-specific disulfide in a crystal, or perhaps a > criteria for assessing specificity? I will do some > functional studies, but I'm looking for some info > on a lazy saturday. > > Thanks in advance. Best- > Todd
