Covid-19 Biological Perspective -Part 2
Apart from the theory of immune system going berserk and causing harm to the Lung cells (https://medium.com/@jain.sm/covid-19-a-biological-perspective-d5ea9cedb517), a new theory from China has emerged.
Inside our red blood cells, there is a molecule called hemoglobin, which contains heme groups. Each heme group is a molecular “ring” (called a porphyrin) that can hold an iron (Fe) ion inside.Having an iron ion inside is what allows this heme to carry O2 (and CO2) in our blood. These RBC transport oxygen to our body parts and carry back CO2 to the lungs to be exchanged again for oxygen.
The viral proteins (non structural ones as discussed in previous article). Let’ visit the role of the non structural proteins once again
Firs lets understand porphyrin. This the molecular ring which is part of the Heme group which are part of the Hemoglobin. In humans, hemoglobin can be degraded into globin and heme. Heme is composed of a porphyrin and an iron ion, and the iron ion is in the middle of the porphyrin.
The computational approach taken to analyse the viral proteins is known as Protein Docking. In laymen’s term this methodology checks which molecule can bind to the protein. The protein in this case is called the receptor or the target and the molecule which binds to the protein is called the Ligand.
The idea here was to see if the Heme binds to the viral Protein.
The results of the docking of structural proteins with Porphyrin were
1. The structural proteins didn’t dock with the Porphyrin directly
2. Was checked whether the structural proteins first removed the iron from Porphyrin and then docked with it. Heme has an oxidase called heme oxidase,which oxidizes heme and dissociates the iron ion. If structural proteins could attack heme and dissociate iron ions, it should have a similar conserved domain as a heme oxidase. No evidence was found for the same. This means the structural proteins were not docking with Porphyrin
The results of the docking of non-structural proteins with Porphyrin were
1. the mechanism by which non-structural proteins attack heme might be: ORF10, ORF1ab and ORF3a attacked heme and generated the porphyrin;
2. ORF6 and ORF7a send porphyrin to ORF8; and ORF8 and the porphyrin formed a stable complex.
This would mean the possibility of the non structural viral proteins colluding to remove the iron from RBC hemoglobin deprives the oxygen carrying capability of RBC and thereby could be leading to deaths.
This theory would imply then that its not the immune system as discussed in last article but the combination of viral proteins which are causing the harm.
Disclaimer- I am not a virologist and , this is just a simple perspective brought out by my readings around the virus and in particular Covid 19 and might not be an 100% accurate account of things.
