this virus also has L455F, it might have the ability of
immune-evading and tighter binding to the ACE2
protein, which is likely to enhance cell entry. The
EG.2 variant is radically different from the others,
and Q52H and F456L mutations make this variant
more similar to the original Omicron which has
greater binding affinity compare to the other XBB
descendants (Veltri et al., 2023)
Our study showed that mutation that has potential
in developing drug resistance remains rare, however
P132H was identified in almost all samples (99.8%).
This result is in line with current global situation
where this mutation is the most prevalent globally.
P132H mutation is exclusively associated with
Omicron because this mutation was identified in
>98% of Omicron (Sacco et al., 2022). On 2022,
P132H was most prevalent in UK (44%), and it was
found in 98% of Omicron subvariant. P132H
mutation is localized at about -22 Å away from the
catalytic site and not in direct contact with any of the
residues of allosteric pocket. Study showed that
P132H got 3CLpro thermal stability compromised
(Lee et al., 2022). A study demonstrated that P132H
mutation alone related to a decreased stability of the
enzyme in vitro. Another study also revealed the
crystal structures shows that the mutations does not
give rise any significant changes of the protein around
the binding pocket or the site of the mutation
(Greasley et al., 2022).
The effect of the P132H mutation on Omicron
3CLpro remains unclear. We found that the binding
affinity of P132H mutant was not significantly
different compared to the wild type. This result was
supported by visualization of hydrogen bond
position, we observed the same position of hydrogen
bond across the mutations. Our result is consistent
with previous study which showed that P132H might
not reduce enzymatic activity and inhibitor binding.
Study showed that P132H decrease thermal stability
of 3CLpro and may cause the increasing protein
flexibility which might broaden substrate profile
substrate profile or to alter ligand binding (Sacco et
al., 2022).
Another study showed that P132H will give effect
to thermal stability only if the proline at position 108
3CLpro is also replaced by other amino acid. Another
impact of P132H was observed by Chen et al.,
Omicron with P132H mutation permitted charged L-
Lys and the enzyme activity is increased toward L-
Trp and L-Tyr compared to the wild type. Catalytic
efficiency was observed on the double mutant K90
and P132H.(Chen et al., 2023) In this study we
observed that P132H alone without other mutation
along with it, therefore P132H alone is considered to
be non-major changes related to the chemical
characteristic of 3CLpro because this mutation does
not play role whether in the active site or the allosteric
binding site of the protein (Ullrich et al., 2022).
4 CONCLUSIONS
NTV is still potent to be used as oral antiviral to treat
COVID-19 in Indonesia, however routine genomic
surveillance is necessary to anticipate the appearance
of mutations that have been proven to be associated
with NTV resistances.
ACKNOWLEDGEMENTS
We gratefully acknowledge all SARS-CoV-2
sequence data contributors in Indonesia, i.e., the
authors and their originating laboratories responsible
for obtaining the specimens, and their submitting
laboratories for generating the genetic sequence and
metadata and sharing via GISAID, on which parts of
this research is based.
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