描述:
Sorting of integral membrane proteins is mediated vesicular trafficking between a variety of organelles. Two sorting signals are tyrosine-based
and dileucine-based signals that interact with heterotetrameric adaptor protein complexes (AP-1, AP-2, AP-3, and AP-4), which are associated
with the vesicle coats. These coatomers contain two large adaptin proteins (
γ,α,δ,ε, andβ1,β2,β3,β4 respectively) that are noncovalently
linked to one medium chain (μ1, μ2, μ3, μ4 respectively) and one small chain (σ1,
σ2,σ3,σ4 respectively). The AP-1 and AP-3 complexes
are involved in protein sorting from the TGN and endosomes, while AP-2, μ2 (AP50) interacts with integral membrane proteins via binding to
tyrosine-based signals with the canonical motif YXXΦ. In addition, AP50/μ2 is required for both the assembly and the proton transport
activity of vacuolar (H+)-ATPases in clathrin coated vesicles. Thus, AP50/μ2 may be involved in targeting integral membrane proteins that are
sorted based on tyrosine-based signals and involved in assembly of functional ion channels associated with clathrin coated vesicles.