Biomedical subjects

Ming-Chuan Wang

Publications and source records attributed to Ming-Chuan Wang.

5 recordsLinked to original sources

PubMed2006

Nanostructure of fibrillin-1 reveals compact conformation of EGF arrays and mechanism for extensibility.

Fibrillin-1 is a 330-kDa multidomain extracellular matrix protein that polymerizes to form 57-nm periodic microfibrils, which are essential for all tissue elasticity. Fibrillin-1 is a member of the calcium-binding EGF repeat family and has served as a prototype for structural analyses. Nevertheless, both the detailed structure of fibrillin-1 and its organization within microfibrils are poorly understood because of the complexity of the molecule and the resistance of EGF arrays to crystallization. Here, we have used small-angle x-ray scattering and light scattering to analyze the solution structure of human fibrillin-1 and to produce ab initio structures of overlapping fragments covering 90% of the molecule. Rather than exhibiting a uniform rod shape as current models predict, the scattering data revealed a nonlinear conformation of calcium-binding EGF arrays in solution. This finding has major implications for the structures of the many other EGF-containing extracellular matrix and membrane proteins. The scattering data also highlighted a very compact, globular region of the fibrillin-1 molecule, which contains the integrin and heparan sulfate-binding sites. This finding was confirmed by calculating a 3D reconstruction of this region using electron microscopy and single-particle image analysis. Together, these data have enabled the generation of an improved model for microfibril organization and a previously undescribed mechanism for microfibril extensibility.

Epidermal Growth Factor↗

PubMed2006

Tissue specific differences in fibrillin microfibrils analysed using single particle image analysis.

Fibrillin microfibrils endow mammalian connective tissues with elasticity and play a fundamental role in the deposition of elastin. The microfibrils are 57 nm periodic supramolecular protein polymers with a mass of 2.5 MDa per repeat. The organisation of molecules within a microfibril is still open to debate and structural studies are only just starting to unravel this issue. The contribution of microfibril associated proteins to microfibril ultrastructure and whether there are any tissue specific differences in microfibril structure is still unknown. Therefore, we have used low dose electron microscopy, single particle image analysis and atomic force microscopy to study the structure of fibrillin microfibrils from different tissues. EM images of microfibrils from aorta, ciliary zonules and vitreous humor were collected and more than 500 microfibril repeats from each sample were subjected to averaging. Averages from each sample were analysed using axial stain exclusion patterns and difference images to detect any variations between them. The overall morphology of fibrillin microfibrils was conserved between tissues and there were only very minor differences in the bead and shoulder region of microfibrils. These data suggest that the structure of isolated microfibrils represents the fibrillin scaffold, and either microfibril associated molecules are lost on purification or play only a minor role in microfibril structure.

Animals↗

PubMed2004

L-type voltage-gated calcium channels: understanding function through structure.

L-type voltage-gated calcium channels (VGCCs) are multisubunit membrane proteins that regulate calcium influx into excitable cells. Within the last two years there have been four separate reports describing the structure of the skeletal muscle VGCC determined by electron microscopy and single particle analysis methods. There are some discrepancies between the structures, as well as reports for both monomeric and dimeric forms of the channel. This article considers each of the VGCC structures in terms of similarities and differences with an emphasis upon translation of data into a biological context.

Animals↗

PubMed2003

The three-dimensional structure of the cardiac L-type voltage-gated calcium channel: comparison with the skeletal muscle form reveals a common architectural motif.

We describe here the first three-dimensional structure of the cardiac L-type voltage-gated calcium channel (VGCC) purified from bovine heart. The structure was determined by electron microscopy and single particle analysis of negatively stained complexes, using the angular reconstitution method. The cardiac VGCC can be isolated as a stable dimer, as reported previously for the skeletal muscle VGCC, with a central aqueous chamber formed by the two halves of the complex. Moreover, we demonstrate that the dimeric cardiac VGCC binds the dihydropyridine [3H]azidopine with a Kd approximately 310 pM. We have compared the cardiac VGCC structure with the skeletal muscle form, determined using the same reconstructive methodology, allowing us to identify common and distinct features of the complexes. By using antibody and lectin-gold labeling, we have localized the intracellular beta polypeptides and the extracellular glycosylation sites of the skeletal muscle VGCC, which can be correlated to the cardiac three-dimensional structure. From the data presented here the assignment of the orientation of the VGCC complexes with respect to the lipid bilayer is now possible. A difference between the cardiac and skeletal muscle ion channels is apparent in the putative transmembrane region, which would be consistent with the absence of the gamma subunit in the cardiac VGCC assembly.

Amino Acid Motifs↗

PubMed2002

3D structure of the skeletal muscle dihydropyridine receptor.

The dihydropyridine receptors (DHPR) are L-type voltage-gated calcium channels that regulate the flux of calcium ions across the cell membrane. Here we present the three-dimensional (3D) structure at approximately 27A resolution of purified skeletal muscle DHPR, as determined by electron microscopy and single particle analysis. Here both biochemical and 3D structural data indicate that DHPR is dimeric. DHPR dimers are composed of two arch-shaped monomers approximately 210A across and approximately 75A thick, that interact very tightly at each end of the arch. The roughly toroidal structure of the two monomers encloses a cylindrical space of approximately 80A diameter, which is then closed on each side by two dome-shaped protein densities reaching over from each monomer arch. The dome-shaped domains have a length of approximately 80-90A and a maximum height of approximately 45A. Small orifices punctuate their exterior surface. The 3D structure disclosed here may have important implications for the understanding of DHPR Ca(2+) channel function. We also propose a model for its in vivo interactions with the calcium release channel at the junctional sarcoplasmic recticulum.

Calcium Channels, L-Type↗