title: Collapsin-1 covalently dimerizes, and dimerization is necessary for collapsing activity.
abstract: Chick collapsin-1, the first identified vertebrate member of the semaphorin family of axon guidance proteins, repels specific growth cones. Like all family members, collapsin-1 contains within its sequence a semaphorin domain that is necessary for specifying activity. Two additional structural domains of collapsin-1, the immunoglobulin (Ig) domain and the basic tail, each potentiate collapsin-1 activity. We identify in this study another structural feature of collapsin-1 that is necessary for its function. Collapsin-1 covalently dimerizes, and dimerization is necessary for collapse activity. This dimerization is mediated through a cysteine at residue 723, between the Ig domain and basic tail. The semaphorin domain alone is not active since it cannot dimerize. The collapsing activity of the semaphorin domain can be reconstituted when made as a chimeric construct with an immunoglobin Fc domain, which promotes dimerization.
authors.affiliation: Department of Neuroscience, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA.
authors.forename: A M
authors.initials: AM
authors.lastname: Koppel
authors.forename: J A
authors.initials: JA
authors.lastname: Raper
mesh_terms: D002851:Chromatography, High Pressure Liquid; D003545:Cysteine / Q000378:metabolism; D019281:Dimerization; D006023:Glycoproteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007141:Immunoglobulin Fc Fragments / Q000378:metabolism; D009414:Nerve Growth Factors / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism; D017354:Point Mutation; D040121:Semaphorin-3A
chemical_list: D006023:Glycoproteins; D007141:Immunoglobulin Fc Fragments; D009414:Nerve Growth Factors; D010446:Peptide Fragments; D040121:Semaphorin-3A; D003545:Cysteine