Product Code Database
Protein G is an immunoglobulin-binding protein expressed in group C and G streptococcal bacteria much like protein A but with differing binding specificities. It is a ~60-kDA (65 kDA for strain G148 and 58 kDa for strain C40) cell surface protein that has found application in purifying antibodies through its binding to the Fab and Fc region. The native molecule also binds albumin, but because serum albumin is a major contaminant of antibody sources, the albumin binding site has been removed from Recombinant DNA forms of protein G. This recombinant protein G, either labeled with a fluorophore or a single-stranded DNA strand, was used as a replacement for secondary antibodies in immunofluorescence and super-resolution imaging.
The protein G B1 domain (aka. GB1) is often used as part of a fusion protein to keep other domains in solution during experiments in solution (e.g. NMR). Many previously insoluble domains have become soluble with the fusion of the GB1 domain. The domain is 56 residues (approx 8kDa) long. On SDS-PAGE gels the GB1 domain runs at roughly 13.5kDa despite being only 8kDa.
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