GRASP55, a second mammalian GRASP protein involved in the stacking of Golgi cisternae in a cell-free system.

Shorter J, Watson R, Giannakou ME, Clarke M, Warren G, Barr FA

We have identified a 55 kDa protein, named GRASP55 (Golgi reassembly stacking protein of 55 kDa), as a component of the Golgi stacking machinery. GRASP55 is homologous to GRASP65, an N-ethylmaleimide-sensitive membrane protein required for the stacking of Golgi cisternae in a cell-free system. GRASP65 exists in a complex with the vesicle docking protein receptor GM130 to which it binds directly, and the membrane tethering protein p115, which also functions in the stacking of Golgi cisternae. GRASP55 binding to GM130, could not be detected using biochemical methods, although a weak interaction was detected with the yeast two-hybrid system. Cryo-electron microscopy revealed that GRASP65, like GM130, is present on the cis-Golgi, while GRASP55 is on the medial-Golgi. Recombinant GRASP55 and antibodies to the protein block the stacking of Golgi cisternae, which is similar to the observations made for GRASP65. These results demonstrate that GRASP55 and GRASP65 function in the stacking of Golgi cisternae.

Keywords:

Hela Cells

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Golgi Apparatus

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Cell-Free System

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Animals

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Humans

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Rats

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Macromolecular Substances

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Membrane Proteins

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Recombinant Proteins

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DNA Primers

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Autoantigens

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Cryoelectron Microscopy

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Cloning, Molecular

,

Amino Acid Sequence

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Base Sequence

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Protein Binding

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Sequence Homology, Amino Acid

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Molecular Sequence Data

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In Vitro Techniques

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Golgi Matrix Proteins