  The observation of the two states $P_c(4380)$ and $P_c(4445)$ [Phys.Rev.Lett.
115 (2015) 072001] solids the existence of the pentaquark state in Nature. In
this work, we study the spectrum of the pentaquark states including one or two
heavy quarks based on the bound state approach by binding the heavy-light
mesons to the nucleon as a soliton in an effective Lagrangian approach. By
regarding the $H$ doublet and $G$ doublet as chiral partners to each other and
coupling them to light mesons with a minimal derivative, the chiral partner
structure of the pentaquark states is calculated. We find that the bound state
approach prefers to arrange $P_c^+(4440)$ and $P_c(4457)$ into a heavy quark
doublet $(\frac{1}{2}^-,\frac{3}{2}^-)$ so both decay to $J/\psi p$ through the
$S$-wave. The predicted spectrum shown in this work serves as a guide for the
experimental hunting of more pentaquark states.
