  We report nucleon mass, isovector vector and axial-vector charges, and tensor
and scalar couplings, calculated using two recent 2+1-flavor dynamical
domain-wall fermions lattice-QCD ensembles generated jointly by the
RIKEN-BNL-Columbia and UKQCD collaborations. These ensembles were generated
with Iwasaki $\times$ dislocation-suppressing-determinant-ratio gauge action at
inverse lattice spacing of 1.378(7) GeV and pion mass values of 249.4(3) and
172.3(3) MeV. The nucleon mass extrapolates to a value $m_N = 0.950(5)$ GeV at
physical point. The isovector vector charge renormalizes to unity in the chiral
limit, narrowly constraining excited-state contamination in the calculation.
The ratio of the isovector axial-vector to vector charges shows a deficit of
about ten percent. The tensor coupling no longer depends on mass and
extrapolates to 1.04(5) in $\overline {\rm MS}$ 2-GeV renormalization at
physical point, in a good agreement with the value obtained at the lightest
mass in our previous calculations and other calculations that followed. The
scalar charge, though noisier, does not show mass dependence and is in
agreement with other calculations.
