Interaction of α_Mβ₂ with Glu-Pg and its derivatives is mediated by theα_MI-domain. The α_MI-domain as a fusion protein with GST at 10 μg/mL in TBS containing 1 mM MgCl₂, 1 mM CaCl₂ in the presence or absence of the P2 peptide (100 μM) was added to microtiter plates coated with 5 μM each Glu-Pg and Pm or 10 μM N-terminal Pg fragment. After incubation for 3 hours at 37° C, anti-GST mAb was added for 1.5 hours. Binding of the α_MI-domain was then detected with a secondary goat antimouse IgG conjugated to alkaline phosphatase, with subsequent development of the reaction with p-nitrophenyl phosphate.