An end effector, comprising: a first jaw member; a second jaw member pivotably coupled to the first jaw member and movable relative to the first jaw member; a drive beam positioned to engage the first jaw member and the second jaw member, the drive beam longitudinally movable through the first and second jaw members; a drive screw defining a longitudinal axis and being supported within the first jaw member, the drive screw including a threaded portion coupled to the drive beam such that rotation of the drive screw imparts longitudinal movement of the drive beam along the second jaw member to move the second jaw member; and a drive link having a proximal engagement portion configured to be coupled to a drive shaft and a distal engagement portion coupled to a proximal end of the drive screw, the drive link being disposed in non-parallel relation to the longitudinal axis of the drive screw.