Consider the question. Is the following sentence factually correct?
"Diphtheria toxin is a single, 90-kDa-molecular weight protein composed of three peptide chains, fragment A, fragment B, and fragment C."
Options:
- yes
- no
 What is the step-by-step reasoning process to arrive at the answer: no?
Diphtheria toxin is a single, 60-kDa-molecular weight protein composed of two peptide chains, fragment A and fragment B.