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
