You might think that as a structural biologist you won't be able to do
much about COVID-19 anytime soon, but that is not true. Yes, real-world
therapeutics and vaccines take time, but we have already seen just how
fast we can get started. There are 21 PDBs already and some even have
bound ligands. Good job Frank et al. BTW! And my personal thanks to
all of you out there who are already hard at work on this.
I believe this forum is an ideal place to share information and ideas on
the structural biology of SARS-CoV-2 as we move forward. It's a big
virus, but there are not that many proteins in it. If all of us
independently do the same bioinformatics and literature searches and end
up trying exactly the same thing in every lab all over the world, then
that would be more than unfortunate. To that end, I am personally
interested on ORF8 for reasons I will go into below. Has anyone tried
to solve it yet? What happened? Didn't express? Bad diffraction?
What? Do tell.
Some of us, as you may have heard, are stuck at home, our beamlines and
labs dark while we shelter-in-place. That doesn't mean our hands are
tied. We are still allowed to think. The fraction of the human race
that has a snowball's chance in Hades of figuring out this bug is very
very small. Structure may be your main skill set, but you are still a
biologist. Do you know how to run a PCR machine? Do you know how to
pipette? You might think that anybody can do it, but that is really not
the case. Ever trained a new student on sterile technique? How many
days did that take? Now remember that your student was no dummy and
already studying biology. Everyone reading this will make an excellent
volenteer at the very least. I'm not saying this to belittle the
average human, only to say that we scientists, moving in the circles we
do, often forget that we have uncommon capabilities.
For example, I also believe we can be useful in assay development. The
void left by the dearth and delay of test results has been filled with
fear, and that is a big problem. The tests, as defined, are
straightforward, but also extremely regimented like any good laboratory
protocol should be. The US CDC's instructions for academic labs are here:
https://www.cdc.gov/coronavirus/2019-nCoV/lab/index.html
My question is: how can this test be made faster, using more commonplace
supplies, in high-throughput mode and still valid? Not just for
clinical but for academic use? I think more than a few people on this
list could be regarded as experts in making a complex biochemical task
faster, more efficient, high-throughput and nonetheless valid. Yes,
there are other people who do virus testing for a living, but right now
they are all rather busy. Maybe if we put our minds to it we can help?
As for why ORF8. I am basing my interest on the bioinformatics done in
this article: https://dx.doi.org/10.1093/nsr/nwaa036. Search for
"T8517C" and you will find what I'm talking about. The authors found
two "types" of SARS-CoV-2. They call them "S" and "L" because the only
conserved amino acid change involved is S84L in ORF8. The "S" type is
believed to be the ancestor of "L". What is interesting is how tightly
linked this mutation is to a silent mutation on the other end of the
genome: the "L" type has a faster codon for Ser in ORF1. Such tight
coupling (r^2=0.945) means there must be significant selective pressure
preventing both of these mutations occurring in the same virus at the
same time. That, I believe, is interesting. Espeically since they are
so far apart I expect this selective pressure might work in trans: as in
a super-infection. That is, the S and L genome types may interfere with
each other.
The authors fall short of claiming evidence of interference upon
super-infection, and indeed they have already been criticised for
calling "L" the "aggressive" type. But it is still interesting and
points a finger at ORF8.
ORF8 has only one homolog in the PDB: 5o32 with 25% identity over a
stretch of 60 residues. This homologous region contains the S84L site
(Val I544 in 5o32). I had a quick look and appears to be a
cavity-filling mutation to me. Not very big, but maybe something could
fit in there. To be sure we'd need a structure of ORF8.
Good luck to you all, and stay healthy.
-James Holton
MAD Scientist
########################################################################
To unsubscribe from the CCP4BB list, click the following link:
https://www.jiscmail.ac.uk/cgi-bin/webadmin?SUBED1=CCP4BB&A=1
