Question

Many proteins have several functions. Provide examples. What natural forces are responsible for this phenomenon?

Answer 1

Proteins are biomolecules composed of many amino acids joined together by peptide bonds to form a tertiary structure. It has varied role in our body, ranging from providing nutrition to catalysing reactions (in the form of enzyms) and also acting as transport carriers and chemical and molecular messengers participating in a communicative relay amongst cells. One protein can perform more than one function, a phenomenon known as protein moonlighting (or gene sharing).

For eg., the E. coli anti-oxidant thioredoxin protein is an example of a moonlighting protein. Upon infection with the bacteriophage T7, E. coli thioredoxin forms a complex with T7 DNA polymerase, resulting in enhanced T7 DNA replication which is a crucial step for successful T7 replication. Thioredoxin binds to a loop in T7 DNA polymerase to bind more strongly to the DNA. The anti-oxidant function of thioredoxin is fully autonomous and fully independent of T7 DNA replication, in which the protein most likely fulfills the functional role.

ADT2 and ADT5 are another example of moonlighting proteins found in plants. Both of these proteins have roles in phenylalanine biosynthesis like all other ADTs. However ADT2, together with FtsZ is necessary in chloroplast division and ADT5 is transported by stromules into the nucleus.

Evolutionary forces are responsible for this phenomenon.