The proteins exhibit four levels of organization:
1. Primary structure: It refers to a sequence of amino acids join together by the peptide bonds to produce a polypeptide chain.
2. Secondary structure: It is a localized twisting of the polypeptide chain by producing a hydrogen bond. Two types are formed, that is, the alpha helix and beta pleated sheet.
3. Tertiary structure: It refers to the three-dimensional composition of a polypeptide chain. The folding is not regular as it is in secondary composition. It produces ionic bonds, hydrophobic interactions, disulfide bond, and hydrogen bond amongst the polypeptide chains.
4. Quaternary structure: It comprises an amalgamation of two or more polypeptide chains that functions as a single functional unit. The bonds are identical as in tertiary composition.
Thus, the levels of secondary, tertiary, and quaternary protein structure would get affected if all the hydrogen bonding associations were inhibited.
Ricin comes under the category of functionally related toxins, in a combination known as RIPs (ribosome inactivating proteins). This disables ribosomes and stops the process of protein synthesis.
They directly associate with and inactivate the ribosomes or modify the factors taking part in the process of translation, generally the elongation step. These proteins bring about depurination of adenine at position 4324 in the 28 S rRNA.
This further inhibits the generation of a critical-stem-loop configuration to which the elongation factor is considered to combine at the time of the translocation step of translation. The ultimate outcome of this activity is the complete inhibition of cellular translation.
