 This view of autoinhibition released by RhoA binding has been challenged by low resolution electron microscopy data showing ROCK to be a constitutive linear dimer 120 nm in length.According to this new data ROCK does not need to be activated by RhoA or phosphorylation because it is always active, and whether ROCK will phosphorylate its substrates (e.g.myosin regulatory light chain) depends only on their subcellular localization.