A surgical instrument comprising: a handle assembly including a housing; an elongated body extending distally from the handle assembly; and a jaw assembly adjacent a distal end of the elongated body, the jaw assembly including: a cartridge assembly including a plurality of fasteners and a longitudinal slot defined therein; an anvil having a fastener forming surface thereon, the cartridge assembly and anvil being mounted for movement with respect to one another between an open position and a closed position in close cooperative alignment for clamping tissue; an actuation sled supported within the cartridge assembly, the actuation sled being movable to urge the plurality of fasteners from the cartridge; a knife blade mounted to the actuation sled; a drive beam including a vertical support strut and a cam member supported on the vertical support strut, the cam member being positioned to translate relative to the anvil to maintain the anvil in the closed position during firing of the fasteners, the vertical support strut being positioned to abut the actuation sled; said surgical instrument being characterized in that it further comprises a mounting portion coupled to the cartridge assembly and the anvil, the anvil being pivotally mounted to the mounting portion for pivotal movement in relation to the cartridge, wherein the anvil includes a pair of actuating shoulders disposed at a proximal end thereof, and wherein the mounting portion includes a pair of biasing members (158a, 158b) biased against the actuating shoulders (157, 159) for pushing the anvil into the open position; and a drive screw supported within the cartridge assembly, the drive screw having a threaded portion, wherein the drive beam is threadably coupled to the threaded portion of the drive screw such that rotation of the drive screw imparts longitudinal movement of the drive beam. a handle assembly including a housing; an elongated body extending distally from the handle assembly; and a cartridge assembly including a plurality of fasteners and a longitudinal slot defined therein; an anvil having a fastener forming surface thereon, the cartridge assembly and anvil being mounted for movement with respect to one another between an open position and a closed position in close cooperative alignment for clamping tissue; an actuation sled supported within the cartridge assembly, the actuation sled being movable to urge the plurality of fasteners from the cartridge; a knife blade mounted to the actuation sled; a drive beam including a vertical support strut and a cam member supported on the vertical support strut, the cam member being positioned to translate relative to the anvil to maintain the anvil in the closed position during firing of the fasteners, the vertical support strut being positioned to abut the actuation sled; said surgical instrument being characterized in that it further comprises a mounting portion coupled to the cartridge assembly and the anvil, the anvil being pivotally mounted to the mounting portion for pivotal movement in relation to the cartridge, wherein the anvil includes a pair of actuating shoulders disposed at a proximal end thereof, and wherein the mounting portion includes a pair of biasing members (158a, 158b) biased against the actuating shoulders (157, 159) for pushing the anvil into the open position; and a drive screw supported within the cartridge assembly, the drive screw having a threaded portion, wherein the drive beam is threadably coupled to the threaded portion of the drive screw such that rotation of the drive screw imparts longitudinal movement of the drive beam.