Abstract
Recently, the gene encoding clathrin assembly protein of lymphoid myeloid leukemia (CALM), which is homologous to the AP180, was cloned from rat brain, and its expression differential to AP180 was reported (Kim and Lee, 1999). This gene product promotes the polymerization of clathrin into clathrin cage and found to be a regulator in membrane trafficking between intracellular compartments in eukaryotic cells (Kim et al., 2000). In this study, we have purified the CALM protein from clathrin-coated vesicles of rat liver using the monoclonal antibody against the recombinant N-terminal region of the CALM. The coated proteins extracted from the coated vesicle fraction was further purified by multi-step procedures involving gel-filtration and ion-exchange chromatography and SDS-PAGE. The purified protein with an apparent molecular weight of 100 kD promoted the assembly of clathrin triskelia into clathrin cage. In this respect the CALM protein bears a functional resemblance to the AP180 that has been previously described.
Highlights
In eukaryotic cells, clathrin-coated vesicles (CCVs) are involved in membrane trafficking of ligands including receptor-mediated intracellular transport, transfer of proteins from trans-Golgi network to pre-lysosomal compartment and recycling of synaptic vesicles (Pearse and Robinson, 1990)
The CCV coat is formed by polymerization of triskelion-shaped clathrin molecules into lattice of clathrin cage, and is catalyzed by the assembly proteins
The clathrin assembly protein of lymphoid myeloid leukemia (CALM) gene was cloned from human leukemia cell line, and was shown to be homologous to the monomeric clathrin adaptor protein of AP180 (Dreyling et al, 1996; Kim and Lee, 1999)
Summary
Clathrin-coated vesicles (CCVs) are involved in membrane trafficking of ligands including receptor-mediated intracellular transport, transfer of proteins from trans-Golgi network to pre-lysosomal compartment and recycling of synaptic vesicles (Pearse and Robinson, 1990). Coated vesicle contains one or more assembly proteins (Robinson, 1994). The assembly protein promotes to assemble clathrin triskelia into artificial clathrin cage that resembles a coated vesicle. The native protein was shown to interact with clathrin triskelia and to induce clathrin assembly into a homogeneous population of 60-70 nm coats (Zhou et al, 1993).
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