Binding of __SP__ __NODE__ protein and immobilized purified mutant __SP__ __NODE__ protein ( deletion 112 1509 with its extracytoplasmic repeat 2 10 deleted and with its extracytoplasmic repeat 1 mutated and with its signal peptide retained I1572T C terminal truncation 1652 End with its extracytoplasmic repeat 12 15 deleted ) from lysate Cos 7 cells does not occur in a cell free system .