Crystallization and preliminary X‐ray analysis of methylamine‐treated α2‐macroglobulin and 3 α2‐macroglobulin‐proteinase complexes

摘要

>Crystals of methylamine‐treated α₂‐macroglobulin (α₂M‐MA), α₂‐macroglobulin in complex with two molecules of trypsin, α₂M‐T2, one molecule of plasmin, α₂‐M‐PL, and one molecule of plasmin followed by methylamine‐treatment, α₂M‐PL(MA), have reproducibly been obtained using ammonium sulfate or magnesium sulfate as precipitants. The crystals are fragile tetragonal bipyramids of up to 1.5 mm in length. Crystals of α₂M‐MA diffracted to at least 9A˚resolution, crystals of α₂M‐T2 diffracted to 10A˚resolution and crystals of α₂M‐PL and α₂M‐PL(MA) diffracted to 11A˚resolution. For α₂M‐MA the cell parameters were determined as:a=b=257A˚,c=555A˚; and for α₂M‐T2 as:a=b=247A˚,c=559A˚. For both preparations the space group was I4(1)22. As estimated from density measurements, the crystals of α₂M‐MA and α₂M‐T2 contain one 360 kDa α₂M dimer per asymmetric unit. The volume of the asymmetric unit/molecular weight,V _m, was estimated at 5.6A˚3/Da. The crystal parameters of α₂M‐PL and α₂M‐PL(MA) were not determined.