Final answer:
FtsZ is the prokaryotic cytoskeletal protein responsible for forming a Z ring during bacterial binary fission, which is critical for cell division in prokaryotes.
Step-by-step explanation:
The cytoskeletal protein expected to be involved in binary fission of a bacterium into two bacteria is FtsZ. FtsZ is a prokaryotic homolog of tubulin proteins that assembles to form a Z ring at the site of cell division. This Z ring is anchored to the plasma membrane and is responsible for pinching the cell envelope, which separates the cytoplasm of the new cells and allows the formation of new cell walls during the binary fission process. Unlike eukaryotic tubulin, which has evolved significantly and forms part of the mitotic spindle fibers, FtsZ is specific to prokaryotes and plays a critical role in prokaryotic cytokinesis.