Figure 8. MPEG reactivity of a cysteine residue present within the SI(+) splice site of the type-I IP₃R.

(A) The Figure shows the rat SI(+) IP₃R sequence terminating at the boundary of fragment I established by N-terminal sequencing of proteolytic fragments [18]. The nine cysteine residues in the tryptic fragment I are shaded and the SI splice site is boxed. (B) COS7 cells were transfected with the C326S mutant of type-I IP₃R and the membranes were treated with 0.5 mM MPEG-20 or MPEG-5 for 5 min before being digested with trypsin for a further 5 min. The fragment I bands were monitored by immunoblotting with NT-1 Ab. Shifted bands are shown by open circles.