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J Struct Biol. 2013 Oct;184(1):43-51. doi: 10.1016/j.jsb.2013.05.006. Epub 2013 May 18.

Clathrin-coated vesicles from brain have small payloads: a cryo-electron tomographic study.

Author information

1
Laboratory of Structural Biology Research, National Institute of Arthritis, Musculoskeletal and Skin Diseases, Bethesda, MD 20892, United States. Electronic address: Bernard_Heymann@nih.gov.

Abstract

Clathrin coats, which stabilize membrane curvature during endocytosis and vesicular trafficking, form highly polymorphic fullerene lattices. We used cryo-electron tomography to visualize coated particles in isolates from bovine brain. The particles range from ∼66 to ∼134nm in diameter, and only 20% of them (all ⩾80nm) contain vesicles. The remaining 80% are clathrin "baskets", presumably artifactual assembly products. Polyhedral models were built for 54 distinct coat geometries. In true coated vesicles (CVs), most vesicles are offset to one side, leaving a crescent of interstitial space between the coat and the membrane for adaptor proteins and other components. The latter densities are fewer on the membrane-proximal side, which may represent the last part of the vesicle to bud off. A small number of densities - presumably cargo proteins - are associated with the interior surface of the vesicles. The clathrin coat, adaptor proteins, and vesicle membrane contribute almost all of the mass of a CV, with most cargoes accounting for only a few percent. The assembly of a CV therefore represents a massive biosynthetic effort to internalize a relatively diminutive payload. Such a high investment may be needed to overcome the resistance of membranes to high curvature.

KEYWORDS:

AP; Adaptor proteins; CB; CV; Clathrin-mediated endocytosis; Cryo-electron microscopy; Fullerenes; Three-dimensional image reconstruction; adaptor protein; clathrin basket; coated vesicle

PMID:
23688956
PMCID:
PMC3796050
DOI:
10.1016/j.jsb.2013.05.006
[Indexed for MEDLINE]
Free PMC Article

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