  The energy shift in molecular spectra due to interaction of nuclear magnetic
quadrupole moment ($M$) with electrons is equal to $\delta E_M = MW_M P_{ M}$,
where $W_M$ is a constant determined by the electronic structure of the
molecule and $P_{ M}$ is a dimensionless constant. We extended the method for
calculation of parity nonconservation effects in triatomic molecules developed
in Ref. [A. Petrov and A. Zakharova, Phys. Rev. A ${\bf 105}$, L050801 (2022)]
to the case of $P_{ M}$ constant and applied it to $^{173}$YbOH in the first
excited $v=1$ bending mode. Results of our calculations are required for the
extraction of the $M$ value from the YbOH experiment.
