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,...

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Bibliographic Details
Published inEuropean journal of cell biology Vol. 45; no. 1; p. 151
Main Authors Taatjes, D J, Chen, T H, Ackerström, B, Björck, L, Carlemalm, E, Roth, J
Format Journal Article
LanguageEnglish
Published Germany 01.12.1987
Subjects
Albumins - analysis
alpha-Amylases - analysis
Animals
Bacterial Proteins
Gold
Humans
Immunoglobulin G - analysis
Immunoglobulins - analysis
Immunologic Techniques
Liver - analysis
Microscopy, Electron
Rats
Specimen Handling
Staphylococcal Protein A
Sucrase-Isomaltase Complex - analysis
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Summary: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.
ISSN:0171-9335