Protein structure

Protein structure refers to the three-dimensional arrangement of atoms in an amino acid-chain molecule. Proteins are polymers – specifically polypeptides – formed from sequences of amino acids, the monomers of the polymer. A single amino acid monomer may also be called a residue indicating a repeating unit of a polymer. Protein structure has a four-level hierarchy: the primary, secondary, tertiary, and quaternary structures.

Primary structure

The primary structure of a protein refers to the sequence of amino acids in the polypeptide chain. The primary structure is held together by peptide bonds, which are made during the process of protein biosynthesis. The sequence of amino acids determines the protein's shape and function. Alterations in the primary structure can significantly affect a protein's properties.

Secondary structure

The secondary structure is the form of local folded structures that form within a polypeptide due to interactions between atoms of the backbone. The most common secondary structures are alpha helices and beta sheets. Hydrogen bonds between the backbone atoms form these structures. Secondary structures are often regionally distinct within the protein and contribute to the overall fold of the protein.

Tertiary structure

The tertiary structure describes the three-dimensional structure of a single protein molecule. The tertiary structure is what determines the protein's function. It is stabilized by various interactions, including hydrogen bonds, ionic bonds, Van der Waals forces, and hydrophobic packing. The tertiary structure can be significantly altered by changes in pH, temperature, and the presence of other molecules, which can lead to protein denaturation.

Quaternary structure

The quaternary structure refers to the structure formed by several protein molecules (polypeptides), often called protein subunits, which function as a single protein complex. Quaternary structures are stabilized by the same non-covalent interactions that stabilize tertiary structures. Proteins with quaternary structures include hemoglobin, DNA polymerase, and ion channels.

Protein folding

Protein folding is the process by which a protein structure assumes its functional shape or conformation. It is a crucial step in the translation of genetic information into functional molecules. Misfolded proteins can lead to diseases such as Alzheimer's, Parkinson's, and prion diseases.

Protein structure prediction

Protein structure prediction is a field of bioinformatics that deals with the prediction of the three-dimensional structure of proteins based on their amino acid sequences. This is important for understanding the function of proteins and for designing new drugs.

See also

• Protein biosynthesis
• Protein domain
• Protein function prediction
• Protein-protein interaction
• Structural biology