Titin: a molecular control freak

Recent studies of the giant protein titin have shed light on ifs roles in m uscle assembly and elasticity and include the surprising findings described here. We now know that the titin kinase domain, which has long been a puzz le, has a novel regulation mechanism. A substrate, telethonin, has been ide ntified that is located over one micron away from the kinase domain in matu re muscle. Single-molecule studies have demonstrated the fascinating proces s of reversible mechanical unfolding of titin. Lastly, and most surprisingl y, it has been claimed that titin controls assembly and elasticity in chrom osomes.