Folding and denaturing don't reorder amino acids
- The idea
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- Why
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The idea
“Folding, heat, pH or crowding can shuffle a protein's amino acids into a new order.”
A denatured protein loses its shape and stops working. With a change that big, it's easy to picture the chain getting scrambled too.
The short version
The mistake: Folding, heat, pH or crowding can shuffle a protein's amino acids into a new order.
What's actually true: The ribosome sets the order from mRNA, and peptide bonds hold it. Folding, heat, pH and crowding only change the shape.
- Primary structure is the amino acid order. The ribosome sets it from the mRNA, joining each amino acid to the next with a covalent peptide bond.
- Hydrogen bonds, ionic attractions, hydrophobic interactions and sometimes disulfide bridges hold the shape. Heat, pH and crowding disrupt the weak ones.
- Adding a phosphate or cutting a finished chain leaves the remaining amino acids in order. A new order needs a different mRNA, like one from a mutated gene.
On the exam: Heat, pH and crowding can change a protein's shape, but never its amino acid order.