Q. A homogeneous protein of native molecular weight 100,000 gave a single band of molecular weight 50,000 on SDS-PAGE in presence of β-mercaptoethanol. N-terminal analysis gave two amino acids alanine and leucine in equal proportions. Hence the

• (A) Protein is a homodimer
• (B) Protein is contaminated with another protein
• (C) Protein has two polypeptides linked by disulphide bridges
• (D) None of the above