extracellular region cytosol plasma membrane zinc ion binding protein ubiquitination synapse ubiquitin protein ligase activity ... KCMF1 is down regulated by high constitutive CD99 (a cell surface glycoprotein) expression in ESFT. KCMF1 expression is ... extracellular region cytosol plasma membrane zinc ion binding protein ubiquitination synapse ubiquitin protein ligase activity ...