Sealing mechanisms are provided. In one embodiment, a system includes a connector configured to couple one or more flow-control valves to equipment installed at a well and an isolation sleeve configured to be retained by the connector. The isolation sleeve may include a seal and a hydraulically actuated piston disposed adjacent one another about a body of the isolation sleeve such that actuation of the piston engages the seal. The isolation sleeve may also include a mechanically driven actuator ring, where the actuator ring energizes a seal against the bore of a tubing hanger. Additional systems, devices, and methods are also disclosed.