Rhomboid-type serine protease that catalyzes intramembrane proteolysis. Can cleave the Drosophila proteins Spitz and Keren (PubMed:16223493). May function in pollen elongation (PubMed:22007993). Cleaves type-1 transmembrane domains using a catalytic dyad composed of serine and histidine that are contributed by different transmembrane domains. Expressed in roots, seedlings, leaves, stems and flowers. No visible phenotype. Belongs to the peptidase S54 family.