Question

Who proposed the ‘signal hypothesis’ meant for the biosynthesis of secretory type of proteins?
A. Baltimore
B. Camillio Golgi
C. Blobel and Sabatini
D. Sheeler and Bianchi

Answer 1

Hint: It was proposed in the year 1975.

Complete answer: David Baltimore is an American virologist who shared the Nobel Prize with Temin for their work in the discovery of reverse transcriptase enzyme and process of reverse transcription.
1. Camillio Golgi was an Italian biologist known for his work on the central nervous system.
He discovered the internal reticular apparatus which was later named as Golgi apparatus from the nerve cells.
2. Sheeler and Bianchi, they are biologists who authored the book cell and molecular biology.
3. Gunter Blobel and David Sabatini proposed the signal hypothesis for the biosynthesis of secretory proteins.

Additional information: Signal hypothesis states that proteins synthesized in the cytoplasm which are targeted to the endoplasmic reticulum.
1. It is directed towards the endoplasmic reticulum following a signal sequence.
2. Secretory protein production requires Golgi bodies and endoplasmic reticulum, two cell organelles present in the cytoplasm for packaging.
3. The proteins which are secretory in nature after their translation into proteins from the mRNA will have to cross the biological membrane to reach their target sites.
4. While transportation these proteins can be disturbed or destroyed due to the action of the biological membranes to prevent this attack these proteins have to be assigned and packaged properly. The secretory proteins which reach the ER are arranged and send to the golgi apparatus for the proper packaging.
5. Golgi bodies give out vesicles containing these secretory proteins for its protection from other denaturing enzymes which might act during its transport.

Hence the correct option is ‘C’.

Note: Blobel and Sabatini presented their signal hypothesis as a “beautiful idea” but there was no experimental data to support the hypothesis.