title: Structural studies of the neural-cell-adhesion molecule by X-ray and neutron reflectivity.
abstract: The structures of adhesion proteins play an important role in the formation of intercellular junctions and the control of intermembrane spacing. This paper describes the combination of neutron and X-ray specular reflectivity measurements to investigate the structure of the ectodomain of the neural-cell-adhesion molecule (NCAM). The measurements with unmodified NCAM suggest the presence of a bend in the extracellular region. Measurements with the polysialic-acid-modified form of NCAM reveal that, at physiological ionic strength, the carbohydrate chains extend beyond the range of the unmodified protein. The excluded volume of the polymer is also ionic-strength-dependent, as expected for a polyelectrolyte. The structural characteristics obtained from these independent analyses of X-ray and neutron reflectivity data agree with each other, with prior reflectivity studies, and with molecular dimensions obtained from direct-force measurements. These results provide structural insights into the configuration of the NCAM ectodomain and the regulation of NCAM adhesion by post-translational modification.
authors.affiliation: Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
authors.forename: Colin P
authors.initials: CP
authors.lastname: Johnson
authors.forename: Giovanna
authors.initials: G
authors.lastname: Fragneto
authors.forename: Oleg
authors.initials: O
authors.lastname: Konovalov
authors.forename: Virginie
authors.initials: V
authors.lastname: Dubosclard
authors.forename: Jean-Francois
authors.initials: JF
authors.lastname: Legrand
authors.forename: Deborah E
authors.initials: DE
authors.lastname: Leckband
mesh_terms: D000818:Animals; D002021:Buffers; D016466:CHO Cells; D006224:Cricetinae; D017666:Deuterium Oxide / Q000737:chemistry; D008051:Lipid Bilayers / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D019006:Neural Cell Adhesion Molecules / Q000737:chemistry* / Q000378:metabolism; D009502:Neutrons; D017434:Protein Structure, Tertiary; D012794:Sialic Acids / Q000737:chemistry / Q000378:metabolism; D012965:Sodium Chloride / Q000737:chemistry; D013057:Spectrum Analysis / Q000379:methods; D020349:Surface Plasmon Resonance; D014162:Transfection; D014965:X-Rays
chemical_list: D002021:Buffers; D008051:Lipid Bilayers; D019006:Neural Cell Adhesion Molecules; D012794:Sialic Acids; C021319:polysialic acid; D012965:Sodium Chloride; D017666:Deuterium Oxide