Localization of classical and alternative pathway regulatory activity within the decay-accelerating factor.

摘要: Decay-accelerating factor (DAF) is a cell-associated C regulatory protein that protects host cells from autologous attack. It functions intrinsically in cell surface membranes to rapidly dissociate classical and alternative pathway C3 convertases whenever these amplifying enzymes assemble on surfaces. composed of four contiguous approximately 70 amino acid long regions termed short consensus repeats (SCRs) share homology with similar units other convertase proteins. attached the membrane by glycoinositol phospholipid (GPI) anchor added posttranslationally. In this study, we prepared rGPI-anchored DAF proteins devoid individual SCRs. We then incorporated GPI-anchored products into sheep erythrocyte (Esh) hemolytic intermediates examined their abilities regulate or activation. found function resides within SCR-2 SCR-3, while SCR-2, -3, -4. Functional comparisons variant fluid phase activation assays established differences reflect domain-specific interactions rather than changes spatial arrangement SCRs above surface. accordance findings, molecules containing SCR-1, -2, but not SCR-4, selectively inhibit