Complex sentence: In molecular biology, the PsbZ (Ycf9) is a protein domain, which is low in molecular weight and a transmembrane protein of in the thylakoid membrane of choloroplasts in cyanobacteria and plants.
Split into simpler sentences: In molecular biology, the PsbZ (Ycf9) is a protein domain, which is low in molecular weight. It is a transmembrane protein and therefore is located in the thylakoid membrane of choloroplasts in cyanobacteria and plants.