Question

What are the 5-side group categories? These are important in how proteins fold

Answer 1

The 5 side group categories are the functional groups present in the side chain of peptide. The interaction and bonding in the peptide or protein sequences is dependent on the class of amino acid they have and also their position.

On the basis of side R group, 5 main classes of amino acids are present in our biological systems.

1. Non polar aliphatic- In this group R side chain consist of hydrocarbon (CH)n e.g., Glycine, alanine, valine, leucine, isoleucine and proline.

2. Aromatic R group- In this aromatic is present. E.g., phenylalanine, tyrosine, tryptophan. they are hydrophobic in nature.

3. Polar uncharged- These amino acids have charged R group but they are hydrophilic in nautre. E.g., serine, theronine, cysteine, methionine, asparagine, glutamine.

4. Polar negatively charged- The side R chain group in COOH group or carboxylic group. Have negative charge in neutral pH. E.g. aspartate and gultamate.

5. Polar positively charged- In this group, amino acid negative charge in neutral pH. They have amino (imino) group in side R group. E.g. arginine, lysine, histidine (imidazole group).

In case of protein folding the side group present in amino acid determine its function.

Hydrophobic group presents in inner region, however, hydrophilic amino acids are present on the surface or active binding site. Cysteine help in the formation of disulfide bridges in tertiary, quaternary structure between two peptides.

The charged amino acids make inter and intra hydrogen bond in the peptides, along with the other noncovalent nad covalent bonding to make stable protein structure.