Skip to content
Login Register

#coat proteins

2 public questions tagged with this topic.

Protein Sorting and Trafficking

The vesicle coat assembly process is initiated by:

Coat assembly regulated spatiotemporally to occur only at correct donor membranes and when cargo present ensuring energy not wasted. Initiating event activation of small GTPases Sar1 and ARF families from GDP cytosolic to GTP membrane state. Sar1 activated by Sec12 GEF integral ER protein exchanges GDP for GTP exposing amphipathic helix embedding ER leaflet inducing curvature recruiting Sec23-Sec24 heterodimer. Similarly ARF1 activated by GBF1 at ERGIC cis-Golgi and BIG1/2 at TGN upon membrane recruitment exposes myristoylated helix plus effector binding switch regions recruiting COPI coatomer

Ref: Lee & Miller, Annu Rev Cell Dev Biol: Sar1 and ARF GTPases initiate coat assembly.

View Details
Protein Sorting and Trafficking

Which coat protein mediates retrograde transport from the Golgi to ER?

Retrieval pathways restoring escaped ER proteins and itinerant SNAREs rely on COPI coat protein complex I heptamer. COPI subunits alpha, beta, beta prime, gamma, delta, epsilon, zeta assemble 600 kDa coatomer. At Golgi cisternae and ERGIC tubules ARF1-GTP generated by GBF1 GEF recruits en bloc coatomer via gamma-beta-delta trunk interaction. Membrane deformation creates 50-60 nm vesicles containing cargo exposing KKXX or KXKXX dilysine motif at C-terminus binding WD40 propeller of alpha and beta prime COP subunits and KDEL receptor-cargo complexes where receptor tail contains KKXX-like signals

Ref: Alberts et al., MBC: COPI coat mediates retrograde Golgi-to-ER transport and retrieval.

View Details