It is a ~60-kDA (65 kDA for strain G148 and 58 kDa for strain C40)[1] 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 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.
An ab initio simulation of the protein G B1 domain demonstrates that, as earlier results suggested, this protein initiates folding via a nucleation event in the hydrophobic core residues followed by small adjustments.
[3] The folding events are as follows: The protein G B1 domain (aka.
On SDS-PAGE gels the GB1 domain runs at roughly 13.5kDa despite being only 8kDa.