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© The Rockefeller University Press,
0021-9525/2000//475 $5.00
The Journal of Cell Biology, Volume 150, Number 3,
, 2000 475-488
Original Article |
Phosphorylation of the Vesicle-Tethering Protein P115 by a Casein Kinase II–Like Enzyme Is Required for Golgi Reassembly from Isolated Mitotic Fragments
graham.warren{at}yale.edu
Coat protein I (COPI) transport vesicles can be tethered to Golgi membranes by a complex of fibrous, coiled-coil proteins comprising p115, Giantin and GM130. p115 has been postulated to act as a bridge, linking Giantin on the vesicle to GM130 on the Golgi membrane. Here we show that the acidic COOH terminus of p115 mediates binding to both GM130 and Giantin as well as linking the two together. Phosphorylation of serine 941 within this acidic domain enhances the binding as well as the link between them. Phosphorylation is mediated by casein kinase II (CKII) or a CKII-like kinase. Surprisingly, the highly conserved NH2-terminal head domain of p115 is not required for the NSF (N-ethylmaleimide–sensitive fusion protein)–catalyzed reassembly of cisternae from mitotic Golgi fragments in a cell-free system. However, the ability of p115 to link GM130 to Giantin and the phosphorylation of p115 at serine 941 are required for NSF-catalyzed cisternal regrowth. p115 phosphorylation may be required for the transition from COPI vesicle tethering to COPI vesicle docking, an event that involves the formation of t-SNARE (trans–soluble NSF attachment protein [SNAP] receptor) complexes.
Key Words: p115 GM130 Giantin CKII tethering
© 2000 The Rockefeller University Press
Abbreviations used in this paper: CKII, casein kinase II; COPI/II, coat protein I/II; GRASP65, Golgi reassembly stacking protein of 65 kD; MGF, mitotic Golgi fragments; NSF, N-ethylmaleimide–sensitive fusion protein; RLG, rat liver Golgi membranes; SNAP, soluble NSF attachment protein; SNARE, SNAP receptor.
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