Protein to Protein Interactions

[bard]

How do protein to protein interactions and/or protein-nucleic acid interactions underlie the cellular processes of Replication, transcription, and metabloism.

Well i know that protein -protein reactions underlie all processes in the cell. For example i think in translation the ribosome is the major player and the ribosome is held together by protein to protein interactions. However what about the other two. I don't understand how the protein to protein interactions and protein-nucleic acid interactions drive metabolism and transcription.

 

[Monique]

Because the proteins together make a functional complex.

Think for instance about transcription factors that bind to DNA. When it is bound, it can recruit the RNA polymerase complex and stabilize that binding to the DNA and thus start transcription. Also, transcription factors can bind to DNA and actually block the access of other factors to the DNA and thus block transcription.

 

[DocToxyn]

A similar role for transcription factors is played out in the metabolism of many chemicals derived from both external or internal sources. In certain cases a cytosolic receptor is activated by a ligand, the ligand/receptor complex then moves to the nucleus, binds to DNA, and promotes the transcription of genes involved in the metabolism of the ligand. Both phase one and phase two metabolism can be mediated by this process. My experience with this stems from bioactivation of chemicals which leads to their metabolism, or bioactivation, from the parent compound to an ultimately more toxic product. An example of this would be benzo[a]pyrene (B[a]P) which is found in things such as cigarette smoke. The parent B[a]P itself is not particularly toxic but the metabolic activation to the dihydrodiol-epoxide, mediated by cytochrome p450 and epoxide hydrolase enzymes, creates a molecule that binds to DNA leading to tumor production. The receptor/transcription factor in this case is the aryl hydrocarbon receptor. As previously stated this metabolic pathway also works on substances produced in the body for specific purposes, such as hormones, and in this case their metabolism is a necessary and beneficial process.