Coronavirus, receptors, SARS, spike proteins and mode of action

Created April 2020 by Bree Latner, Offline version here
Video by Catalyst University on their YouTube channel.

    Coronaviruses are a class of viruses that have a large protein coat known for having spike proteins on the surface giving it the name corona. They cause or SARS, this is also known as Coronavirus Disease or COVID. Coronaviruses have a genome composed of one strand of RNA that is about 30,000 nucleotides long. This genomic RNA strand in coronaviruses is a strand so we call that genomic RNA(+). This means the strand contains the code needed to translate the viral proteins directly without transcription. To get inside of the host cell, viral bind with the CAECAM1 receptors on the cell surface of the host cell. This causes receptor-mediated to take the virus into the host cell. Once inside the virus is disassembled thought a process called to release the viral genomic RNA+ strand into the cytoplasm of the host cell. Once in the cytoplasm the viral genomic RNA(+) strand is into polyproteins by the host's ribosomes. The first open reading from of the RNA(+) strand produces two , PP1a and PP1ab. The two polyproteins are produced from the same open reading frame, ORF1 because of . The polyproteins are produced by the translation of the ORF1a section of ORF1. The polyproteins are produced by the translation of both the ORF1a section and the ORF1b section of ORF1. The polyproteins made by translating the ORF1 region of the genomic RNA(+) strand are broken apart into replicase and transcriptase proteins through . One of those proteins, RNA-dependent RNA polymerase, then replicates the RNA(+) strand to form the RNA(-) strand. The proteins transcribe the genomic RNA(-) strand into many different subgenomic mRNAs that encode the instructions for viral structural proteins. This occurs because the RNA(-) strand contains many that allow for transcription to start in multiple places. This creates subgenomic of varying lengths which code for the various viral structural proteins. The subgenomic mRNAs are translated into viral proteins which will be assembled to form a new viral capsid. The translation of the viral structural proteins occurs in the ribosomes embedded in the . From here, the viral structural proteins and genomic RNAs are sent through the pathway to leave the host cell. The viral structural proteins and genomic RNAs are sent to the which will assemble them and package them. The viral structural proteins are formed into a protein capsid enclosing genomic RNA+ strands to form , which are viral progeny that are vectors for the infection. The Golgi will then package the virions into which will be sent to the plasma membrane. The virions exit the cell via when the vesicle fuses with the plasma of the host cell which transports the virions out of the cell on to infect other host cells.