Protein folding is the biological process by which a polypeptide chain assumes its large-scale, three-dimensional shape.

Protein Folding

In protein tertiary structure, an ionic bond is an attraction that occurs between a positively charged amino acid and a negatively charged amino acid. These ionic interactions work to hold loops of the polypeptide backbone in place.

Ionic Bonds in Protein Tertiary Structure

In protein tertiary structure, hydrophobic interactions occur when hydrophobic amino acids, which contain only carbon and hydrogen atoms, cluster together. This clustering helps hold loops of the polypeptide backbone in place.

Hydrophobic Interactions in Protein Tertiary Structure

In protein tertiary structure, a disulfide linkage is a covalent bond formed when the sulfur atom of one amino acid binds to the sulfur atom of another. This linkage helps hold loops of the polypeptide backbone in place.

Disulfide Linkages in Protein Tertiary Structure

In protein tertiary structure, a hydrogen bond is an attraction between two polar amino acids. These attractions help hold loops of the polypeptide backbone in place.

Hydrogen Bonds in Protein Tertiary Structure

The tertiary structure of a protein is the large-scale, three-dimensional shape of a single polypeptide chain. This conformation is determined by various interactions between amino acid residues that are far apart in the chain, including disulfide bridges (covalent bonds between sulfhydryl, or $$-\text{SH}$$, groups of side chains), hydrogen bonds, ionic bonds, and hydrophobic interactions.

Google

University of Southern Mississippi

A protein's structure is organized into four hierarchical levels that determine its three-dimensional conformation and function:

1. Primary structure: The specific sequence of a chain of amino acids.
2. Secondary structure: The local folding of the polypeptide chain into shapes such as helices (like the $$\alpha$$-helix) or sheets (like the $$\beta$$-pleated sheet).
3. Tertiary structure: The three-dimensional folding pattern of a single polypeptide chain due to interactions between side chains.
4. Quaternary structure: The configuration formed when a protein consists of more than one polypeptide chain (subunit).

Levels of Protein Structure

https://openstax.org/details/books/microbiology/

Microbiology covers the scope and sequence requirements for a single-semester microbiology course for non-majors. The book presents the core concepts of microbiology with a focus on applications for careers in allied health. The pedagogical features of the text make the material interesting and accessible while maintaining the career-application focus and scientific rigor inherent in the subject matter. Microbiology’s art program enhances students’ understanding of concepts through clear and effective illustrations, diagrams, and photographs.

Microbiology is produced through a collaborative publishing agreement between OpenStax and the American Society for Microbiology Press. The book aligns with the curriculum guidelines of the American Society for Microbiology.

OpenStax Microbiology Textbook

The primary structure of a protein is the specific sequence of amino acids that make up its polypeptide chain. This linear sequence of amino acids has a free amino group (N-terminus) at one end and a free carboxyl group (C-terminus) at the other.

Primary Structure

Tertiary Structure

The quaternary structure of a protein is the overall multi-subunit configuration formed by the assembly of several separate polypeptide chains (protein subunits), which must all be present and correctly configured for the protein to function. This overall quaternary structure is stabilized by relatively weak interactions.

Quaternary Structure

A protein's secondary structure is the localized folding of a sufficiently long polypeptide chain into shapes such as helices and sheets. This folding is stabilized by hydrogen bonds between the amine and carbonyl functional groups of the peptide backbone, excluding the variable R side chain. The most common types of secondary structure are the $$\alpha$$-helix and $$\beta$$-pleated sheet.

Learn Before

Related

Learn After