Streptococcal protein G-gold complex: comparison with staphylococcal protein A-gold complex for spot blotting and immunolabeling.
Protein G, a cell wall protein isolated from human group G streptococci strain G148, binds in a similar manner as protein A from Staphylococcus aureus to the Fc portion of IgG molecules. Indeed, protein G has been proposed as a superior Fc binding protein due to its broader species reactivity. Thus, we have prepared a complex of protein G with particles of colloidal gold and determined its applicability for spot-blot analysis and postembedding immunolabeling by comparing it with protein A-gold complex. By spot-blot analysis no difference in binding of protein G-gold or protein A-gold to IgG molecules from a whole spectrum of animal species was observed. Moreover, using rabbit, sheep, or goat anti-rat albumin antibodies to detect nitrocellulose-immobilized rat albumin or antigenic sites in paraffin and Lowicryl K4M thin sections from rat liver, no difference was found with protein G-gold or protein A-gold. Similarly, no difference in binding to protein G-gold or protein A-gold was observed with a battery of monoclonal antibodies. However, in contrast to expectations, protein A-gold reacted well with both sheep and goat IgG molecules; indeed, for the light and electron microscopic localization of albumin with sheep or goat antibodies it was as efficient as protein G-gold. These results demonstrate, therefore, that both protein G-gold and protein A-gold are useful second step reagents for immunolabeling and that protein G-gold was not a superior probe in the systems tested.
Taatjes
D J
DJ
Interdepartmental Electron Microscopy, University of Basle, Switzerland.
Chen
T H
TH
Ackerström
B
B
Björck
L
L
Carlemalm
E
E
Roth
J
J
D000418:Albumins / Q000032:analysis; D000818:Animals; D001426:Bacterial Proteins; D006046:Gold; D006801:Humans; D007074:Immunoglobulin G / Q000032:analysis; D007136:Immunoglobulins / Q000032:analysis*; D007158:Immunologic Techniques; D008099:Liver / Q000032:analysis; D008854:Microscopy, Electron; D051381:Rats; D013048:Specimen Handling; D013205:Staphylococcal Protein A; D013394:Sucrase-Isomaltase Complex / Q000032:analysis; D000516:alpha-Amylases / Q000032:analysis
D000418:Albumins; D001426:Bacterial Proteins; C034284:IgG Fc-binding protein, Streptococcus; D007074:Immunoglobulin G; D007136:Immunoglobulins; D013205:Staphylococcal Protein A; D006046:Gold; D013394:Sucrase-Isomaltase Complex; D000516:alpha-Amylases