Question

Classify each protein example according to its highest level of protein structure. 

When performing site-directed mutagenesis to test predictions about which residues are essential for protein function, wh amino acid substitution would disrupt protein structure the most. 

Answer 1

Primary Structure

Amino acid sequence of myoglobin

Secondary Structure

the C-helix of a -lactalbumin

Tertiary Structure

A single hemoglobin subunit with heme

Quaternary Structure

Hemoglobin

Aminoacid sequences of a protein are generally called as their primary structure as they are primarily responsible for their entire structure. Hence the amino acid sequence of myoglobin is the primary structure.

The intermediate forms of a protein formed before they fold are their secondary structures. Alpha helix and beta pleated sheets are the most common secondary structures. Hence the C helix of alpha-lactalbumin is the secondary structure.

The tertiary structure of a protein is the structure of its single polypeptide chain with its secondary structures. Hence a single hemoglobin subunit with heme is it's tertiary structure.

Quaternary structure is the assemblage of multiple folded units of a protein into a multi-subunit complex. Hemoglobin is one of this kind of structures. Hence hemoglobin is a quaternary structure.