A nickel, iron, iron-sulfur protein. The enzyme from the archaeon Pyrococcus furiosus is part of a heterotetrameric complex where the ¦Á and ¦Ä subunits function as a hydrogenase while the ¦Â and ¦Ã subunits function as sulfur reductase (EC 1.12.98.4, sulfhydrogenase). Different from EC 1.12.1.3, hydrogen dehydrogenase (NADP+).