Protein Structure
Amino acids are covalently joined via peptide bonds to form long chains called polypeptides.
The order of the amino acid sequence is called the primary structure and determines the way the chain will fold
Amino acid sequences will commonly fold into two stable configurations, called secondary structures.
Both α-helices and β-pleated sheets result from hydrogen bonds forming between non-adjacent amine and carboxyl groups.
Amino acids are covalently joined via peptide bonds to form long chains called polypeptides.
The order of the amino acid sequence is called the primary structure and determines the way the chain will fold
- Different amino acid sequences will fold into different configurations due to the chemical properties of the variable side chains
Amino acid sequences will commonly fold into two stable configurations, called secondary structures.
- Alpha helices occur when the amino acid sequence folds into a coil / spiral arrangement
- Beta-pleated sheets occur when the amino acid sequence adopts a directionally-oriented staggered strand conformation
Both α-helices and β-pleated sheets result from hydrogen bonds forming between non-adjacent amine and carboxyl groups.
- Where no secondary structure exists, the polypeptide chain will form a random coil
Secondary Structure – Alpha Helices versus Beta Pleated Sheets
The overall three-dimensional configuration of the protein is referred to as the tertiary structure of the protein.
The tertiary structure of a polypeptide chain will be determined by the interactions between the variable side chains
The affinity or repulsion of side chains will affect the overall shape of the polypeptide chain and are determined by the position of specific amino acids within a sequence
The tertiary structure of a polypeptide chain will be determined by the interactions between the variable side chains
- These interactions may include hydrogen bonds, disulphide bridges, ionic interactions, polar associations, etc.
The affinity or repulsion of side chains will affect the overall shape of the polypeptide chain and are determined by the position of specific amino acids within a sequence
- Hence, the order of the amino acid sequence (primary structure) determines all subsequent levels of protein folding.