Protein Structure

There are four levels of protein structure:

1. Primary

2. Secondary

3. Tertiary

4. Quaternary

Primary Structure

The primary structure of a protein is its linear amino acid sequence.

Secondary Structure

The secondary structures of a protein refer to the ways in which local segments of its primary structure fold on themselves.

  There are a variety of different secondary structural elements; the most common of these are alpha helices and beta sheets.

Alpha Helices

These right-handed helices are common motifs in protein secondary structure.

Beta Sheets

Beta sheets are pleated sheets consisting of beta strands laterally connected by at least 2-3 backbone hydrogen bonds.


Tertiary Structure

The tertiary structures of a protein are the local three-dimensional shapes its secondary structure folds on itself to create.

Quaternary Structure

Quaternary structure refers to the arrangement and number of multiple protein subunits comprising a multi-subunit complex.