title: Protein AG-gold complex: an alternative probe in immunocytochemistry.
abstract: The purpose of this study was to evaluate the use of protein AG tagged with colloidal gold as a reliable immunocytochemical reagent. Protein AG is a recombinant of 47.3 KD molecular weight and pI = 4.3, which displays immunoglobulin Fc binding sites for both staphylococcal protein A and streptococcal protein G. It adsorbs to 10-nm colloidal gold particles with a lower affinity than does protein A, and is saturable. A maximal number of 12 protein AG molecules could be accommodated on the gold particle surface. Protein AG-gold conjugates yielded positive signals in post-embedding immunocytochemical assays when used as a secondary reagent in conjunction with several species and classes of polyclonal (rabbit, goat, sheep, guinea pig) and mouse monoclonal immunoglobulins (IgG1, IgG2, and IgG3). In addition, protein AG-gold was found to be a useful reagent in immunoblot analysis because of its ability to bind and identify nitrocellulose-immobilized IgGs (rabbit, mouse, goat, sheep, rat, and cow). Its spectrum of specificity towards various types of antibodies combines those of the parental protein A and protein G molecules. The protein AG-gold complex therefore appears to be a highly versatile and convenient alternative probe for immunochemical and immunocytochemical studies.
authors.affiliation: Département d'Anatomie, Université de Montréal, Québec, Canada.
authors.forename: L
authors.initials: L
authors.lastname: Ghitescu
authors.forename: Z
authors.initials: Z
authors.lastname: Galis
authors.forename: M
authors.initials: M
authors.lastname: Bendayan
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D006046:Gold / Q000737:chemistry*; D017979:Gold Colloid; D006863:Hydrogen-Ion Concentration; D015151:Immunoblotting; D007136:Immunoglobulins / Q000378:metabolism; D007150:Immunohistochemistry / Q000379:methods*; D007700:Kinetics; D009942:Organometallic Compounds / Q000737:chemistry* / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry* / Q000378:metabolism; D013205:Staphylococcal Protein A / Q000737:chemistry* / Q000378:metabolism; D013291:Streptococcus
chemical_list: D001426:Bacterial Proteins; D017979:Gold Colloid; C034284:IgG Fc-binding protein, Streptococcus; D007136:Immunoglobulins; D009942:Organometallic Compounds; D011994:Recombinant Proteins; D013205:Staphylococcal Protein A; C070001:protein AG-gold complex; D006046:Gold