  A mismatch of atomic registries between single-layer transition metal
dichalcogenides (TMDs) in a two dimensional van der Waals heterostructure
produces a moir\'e superlattice with a periodic potential, which can be
fine-tuned by introducing a twist angle between the materials. This approach is
promising both for controlling the interactions between the TMDs and for
engineering their electronic band structures, yet direct observation of the
changes to the electronic structure introduced with varying twist angle has so
far been missing. Here, we probe heterobilayers comprised of single-layer
MoS$_2$ and WS$_2$ with twist angles of $(2.0 \pm 0.5)^{\circ}$, $(13.0 \pm
0.5)^{\circ}$, and $(20.0 \pm 0.5)^{\circ}$ and investigate the differences in
their electronic band structure using micro-focused angle-resolved
photoemission spectroscopy. We find strong interlayer hybridization between
MoS$_2$ and WS$_2$ electronic states at the $\bar{\mathrm{\Gamma}}$-point of
the Brillouin zone, leading to a transition from a direct bandgap in the
single-layer to an indirect gap in the heterostructure. Replicas of the
hybridized states are observed at the centre of twist angle-dependent moir\'e
mini Brillouin zones. We confirm that these replica features arise from the
inherent moir\'e potential by comparing our experimental observations with
density functional theory calculations of the superlattice dispersion. Our
direct visualization of these features underscores the potential of using
twisted heterobilayer semiconductors to engineer hybrid electronic states and
superlattices that alter the electronic and optical properties of 2D
heterostructures.
