Recombinant Protein A/G Protein

A: This is a product from one of our sister brands and their lab has just cloned the protein chimera but no further characterization studies were performed. My advice for you would be to search available literature on Protein and G binding sites characterization.  Since this Protein AG has all binding sites from both A and G proteins I think the initial characterization of these proteins should apply. I've tried to find the answer for you and the most relevant data I was able to find comes from Moks et al. 1986 publication (Eur. J. Biochem. 1986. 156,637-643). Basically, the sequences of the binding sites are highly homologous: ABC are identical and D and E differ in 2-3 aminoacids (Fig1). That gives the first clue that the binding specificity will likely be very similar. Later on they show the binding capacity of sites E and B, concluding that the site E has lower binding affinity than B, and they postulate that that the differences in binding affinity of sites A, B, C and D may exist, however are not great. To my understanding it is enough to conclude (assuming the same is true for Protein G) that all sites will be able to bind the same type of IgG, although with somewhat different affinity. There is however an earlier paper that may be of interest to you - Langone et al.  1978 (J Immunol 1978; 121:333-338; ;). These researchers report that intact Protein A, despite having 4 binding sites (now we now there are actually 5), can only bind 2 molecules of IgG.