The present investigations are focusing on drug-development, which are especially targeting large molecules and particularly proteins as therapeutic options. Production of protein formulations can be major challenge. Gathering and providing information about proteins and their different structures may be the direct way to produce site-specific targeting drugs. However, without a good knowledge on nature of protein structure and the conformational characteristics of the specific protein, production of particular drugs will become very difficult task. These technical brief ideas can give the researchers to get quick overview of protein structure and mechanism of action. In this article, we are providing the brief information on structure of proteins. It will also cover how protein structure can be affected during formulation and some of the analytical methods which can be used both to determine the protein structure and analyze the protein stability.
The term structure when used in relation to proteins, takes on a much more complex meaning than it does for small molecules. Proteins are macro-molecules and have four different levels of structures – Primary, Secondary, Tertiary and Quaternary.
1) Primary structure: It represent the linear amino acid structure
2) Secondary structure: Local folding of amino acids in primary structure
3) Tertiary structure: Global folding of peptide strand
4) Quaternary structure: Interactions between two subunits and leads to binding of two subunits form the functional proteins
Changes in protein coding sequence of gene can have the following effects
1) Silent mutation: This accurse when one codon is replaced by another codon that can specify (coding) the same amino acid. This replacement will not change the amino acid sequence of the protein, so function of protein will be remaining same.
2) Missense substitution (point mutation): In this substitution a sense codon specifying a particular amino acid is substituted by a sense codon specifying other amino acid. This substitution can change the amino acid sequence of the protein.
3) Nonsense substitution: In this substitution a sense codon specifying an amino acid is substituted by a termination or stop codon that result into premature termination of translation. This mutation will lead to the formation of truncated protein. Truncated protein may behave like a uncontrollable elements.
Determination of amino acid sequence in a protein can be used to identify the primary structure of that protein. It is the only structure show the strongly stabilized by covalent interactions at structural level. However, the amino acid sequence at primary structural level does not contain any non-covalent interactions. The covalent interactions in peptide present at between two amino acids. The primary structure will be formed by covalent interaction between α- carboxylic and α- amino group of the amino acids. The side chains of the amino acids do not participate in the primary structure formation.