Choose an example to explain the role of G proteins in protein transport (Protei
ID: 274278 • Letter: C
Question
Choose an example to explain the role of G proteins in protein transport (Protein trafficking, Chapter 15). 1) As a protein is made, the polypeptide is in an extended conformation, with every amino acid exposed to the aqueous environment. Although both polar and charged side chains can mix readily with water, this is not the case for nonpolar side chains. Explain how ) s hydrophobic interactions may play a role in the early stages of protein folding, and have i C 'sí an influence on the final protein conformation. 3) Propose mechanism(s) explaining why unfavorable reactions can o?cur inside the cells while they would not occur in a test tube. many nnyyExplanation / Answer
1)Rab, ARF proteins are monomeric small G-proteins belongs to Ras superfamily. These proteins present in two alternate states, GTP binding and GDP binding. They utilise GTP as an energy source to carry proteins to their destinations in membrane trafficking. They involved in vesicle formation, and its movement on cytoskeletal elements actin, myosin. These vesicles have proteins inside and transported from rough endoplasmic reticulum where they produced to other targets like cytosol and cell membrane via Golgi complex.
2) In the primary structure of the protein, there will be an extended stretch of amino acids produced on the endoplasmic reticulum. The hydrophobic and hydrophilic amino acids together decide the protein conformation. The hydrophilic amino acids can be exposed to the aqueous environment while hydrophobic amino acids strongly rippled by it. so they play a key role in protein secondary structure in which the amino acid chain will fold in such a way that hydrophilic amino acid faces the aqueous environment and hydrophobic amino acids may remain in the grove to avoid an aqueous environment in cell and vice-versa. the secondary structure of a protein has either alfa helix or beta pleated sheets, both of which are amphipathic having hydrophilic and hydrophobic amino acids in them.
3) there are many unfavourable reactions occur inside the cell which is not possible in physiological conditions, those do not spontaneously occur but need external energy to carry forward, for example, some reactions in replication of DNA transcription and translation are thermodynamically unfavourable. they couple with hydrolysis of ATP, rarely GTP to release energy.
The other unfavourable reactions not coupled with ATP hydrolysis like transport in the cell may be coupled with carrier proteins, enzymes, and concentration gradients.
These unfavourable reactions are not possible in a test tube where the environment and external energy support is not possible.