title: Substrate-dependent morphology of supramolecular assemblies: fibrillin and type-VI collagen microfibrils.
abstract: Substrate hydrophobicity/hydrophilicity has previously been shown to affect the morphology and biological function of isolated proteins. We have employed atomic force microscopy to investigate substrate dependent morphologies of two biochemically distinct native supramolecular assemblies: fibrillin and type-VI collagen microfibrils. These morphologically heterogeneous microfibrillar systems are found in many vertebrate tissues where they perform structural and cell-signaling roles. Fibrillin microfibrils adsorbed to a hydrophilic mica substrate adopted a diffuse morphology. Fibrillin microfibrils adsorbed to mica coated with poly-L-lysine or to borosilicate glass substrates had a more compact morphology and a directional asymmetry to the bead, which was not present on mica alone. Intermediate morphologies were observed along a substrate gradient. The classical double-beaded appearance of type-VI collagen microfibrils was evident on mica coated with poly-L-lysine and on glass. On hydrophilic mica, morphology was severely disrupted and there was a major conformational reorganization along the whole collagen microfibril repeat. These observations of substrate dependent conformation have important implications for the interpretation of data from in vitro protein interaction assays and cellular signaling studies. Furthermore, conformational changes may be induced by local charge environments in vivo, revealing or hiding binding sites.
authors.affiliation: Wellcome Trust Centre for Cell-Matrix Research, School of Biological Sciences, University of Manchester, Manchester, M13 9PT, United Kingdom. michael.sherratt@man.ac.uk
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Sherratt
authors.forename: David F
authors.initials: DF
authors.lastname: Holmes
authors.forename: C Adrian
authors.initials: CA
authors.lastname: Shuttleworth
authors.forename: Cay M
authors.initials: CM
authors.lastname: Kielty
mesh_terms: D008841:Actin Cytoskeleton; D000538:Aluminum Silicates; D000818:Animals; D001665:Binding Sites; D002417:Cattle; D003094:Collagen; D024141:Collagen Type IV / Q000737:chemistry*; D003285:Contractile Proteins; D005123:Eye / Q000378:metabolism; D000071837:Fibrillins; D005898:Glass / Q000737:chemistry; D006031:Glycosylation; D007091:Image Processing, Computer-Assisted; D020894:Microfibrils / Q000737:chemistry*; D008840:Microfilament Proteins / Q000737:chemistry*; D018625:Microscopy, Atomic Force; D011107:Polylysine / Q000737:chemistry; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D015398:Signal Transduction; D013379:Substrate Specificity; D013997:Time Factors
chemical_list: D000538:Aluminum Silicates; D024141:Collagen Type IV; D003285:Contractile Proteins; D000071837:Fibrillins; D008840:Microfilament Proteins; D011107:Polylysine; D003094:Collagen; C011934:mica