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Molecular structure and flexibility of the yeast coatomer as revealed by electron microscopy.

ABSTRACT: Coat protein complex I (COPI)-coated vesicles, one of three major types of vesicular carriers in the cell, mediate the early secretory pathway and retrograde transport from the Golgi to the endoplasmic reticulum. COPI vesicles are generated through activation of the regulatory GTPase Arf1 at the donor membrane and the subsequent recruitment of coatomer, a coat protein complex consisting of seven stably associated components. Coatomer functions in binding and sequestering cargo molecules and assembles into a polymeric protein shell that encompasses the surface of COPI vesicles. Little is known about the structural properties of this heptameric complex. We have isolated native yeast coatomer and examined its structure and subunit organization by single-particle electron microscopy. Our analyses provide the first three-dimensional picture of the complete coatomer and reveal substantial conformational flexibility likely to be critical for its scaffolding function.

SUBMITTER: Yip CK

PROVIDER: S-EPMC3096150 | biostudies-literature | 2011 May

REPOSITORIES: biostudies-literature

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Molecular structure and flexibility of the yeast coatomer as revealed by electron microscopy.

Yip Calvin K CK Walz Thomas T

Journal of molecular biology 20110322 5

Coat protein complex I (COPI)-coated vesicles, one of three major types of vesicular carriers in the cell, mediate the early secretory pathway and retrograde transport from the Golgi to the endoplasmic reticulum. COPI vesicles are generated through activation of the regulatory GTPase Arf1 at the donor membrane and the subsequent recruitment of coatomer, a coat protein complex consisting of seven stably associated components. Coatomer functions in binding and sequestering cargo molecules and asse ...[more]

PMID: 21435344

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Project description:The protein is naturally dynamic and heterogeneous in solution. Protein dynamics involves both equilibrium fluctuations that regulate biological function and other non-equilibrium effects of biological motors, which convert chemical energy to mechanical energy. However, a single, unique structure of protein determined from X-ray crystal and conventional single-particle electron microscopy is insufficient to encompass the dynamic nature of proteins in solution. Structure determination of dynamic and heterogeneous protein is essentially required the determination of each individual particle of protein. Recently, Drs. Gang Ren and Lei Zhan published the first single molecule three-dimensional (3D) EM images of individual proteins ever obtained with enough clarity to determine their structure, an IgG antibody (14 Å resolution) and a 17nm HDL (36 Å resolution). These results depended upon four innovations: i) improved cryo-electron microscopy (cryoEM) sample preparation and Electron microscopy (EM) operation conditions resulted in the successful imaging of a 17 nm HDL particle (120-200kDa) by cryo-electron tomography (cryoET); ii) developed an optimized NS (OpNS) protocol that eliminates the rouleau artifact that has plagued EM research for three decades. This OpNS protocol provides high-contrast single lipoprotein images with similar size (<5%) and shape (<5%) to that seen by cryoEM; iii) developed a high-resolution and high contrast sample preparation protocol, cryo-positive-staining (cryoPS) that allows direct visualization of the secondary structure of a small protein, such as the β-strands in CETP and the helical double belt of apoA-I in spherical HDL; iv) developed a robust tomography reconstruction method, Individual Particle Electron Tomography (IPET) that is a high-resolution, high throughput reconstruction method that, to the best of our knowledge, is the only method for determining an individual protein structure. Remarkably, IPET went against the conventional wisdom that a single protein can NOT be reconstructed by EM and this opens a door for the study of protein dynamics via a particle-by-particle structural comparison.

Dataset Information

Molecular structure and flexibility of the yeast coatomer as revealed by electron microscopy.

Publications

Molecular structure and flexibility of the yeast coatomer as revealed by electron microscopy.

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