Q.3 Protein A, which has strong affinity to Fc region of immunoglobulin, is extracted from
(A)Saccharomyces cerevisiae
(B)Staphylococcus aureus
(C)Streptococcus pyogenes
(D)Streptococcus sanguis
Protein A, renowned for its high-affinity binding to the Fc region of immunoglobulins, originates from a key bacterial pathogen. This MCQ probes microbiology knowledge essential for biotech, immunology, and antibody purification studies.
Correct Answer
(B) Staphylococcus aureus produces Protein A, a 42 kDa surface protein encoded by the spa gene. It binds IgG Fc domains, aiding immune evasion and widely used in affinity chromatography for antibody purification.
Option Explanations
(A) Saccharomyces cerevisiae
S. cerevisiae, a yeast, expresses Protein A recombinantly for biotech production but does not naturally produce it. Native extraction occurs from bacterial sources.
(C) Streptococcus pyogenes
S. pyogenes produces streptococcal Protein G, which binds IgG Fc and Fab regions, but lacks Protein A. Protein G serves analogous immune evasion roles.
(D) Streptococcus sanguis
S. sanguis expresses Protein G homologs but not Protein A. It colonizes oral mucosa without the characteristic Fc-binding of staphylococcal Protein A.
Applications in Biotechnology
Protein A sepharose columns exploit its specificity for IgG purification from sera or ascites. Cowan I strain of S. aureus provides a natural source, revolutionizing monoclonal antibody production.
