title: The structure of immunoglobulin variable regions in the horned shark,Heterodontus francisci.
abstract: The heavy and light chains of pooled antibodies of the hybodont shark,Heterodontus francisci (horned shark), were subjected to amino acid sequence analysis. Yield determinations showed that more than 90% of the available polypeptides in the respective pools were sequenced. The heavy chains were homogeneous in the initial framework segment and showed a sequence homology of approximately 70% with the corresponding region of the more recently evolved nurse shark and a 45% homology with a human myeloma heavy chain. The light chains were less homogeneous and not identifiable as either kappa or lambda chains as known in higher species. The first half-cystine characteristics of the variable domain intrachain disulfide bridge of immunoglobulins was present in the same position (22 for heavy chains; 23 for light chains) in the horned shark as in mammalian species. The sequence analysis also suggested the presence of a hypervariable region in the horned shark light chains. The combined data imply that the antigen-binding function of immunoglobulins is mediated in much the same manner in this primitive shark as in more recently evolved species, including mammals.
authors.affiliation: The Northeastern Ohio Universities College of Medicine, 44272, Rootstown, Ohio.
authors.forename: J M
authors.initials: JM
authors.lastname: Kehoe
authors.forename: J
authors.initials: J
authors.lastname: Sharon
authors.forename: B
authors.initials: B
authors.lastname: Gerber-Jenson
authors.forename: G W
authors.initials: GW
authors.lastname: Litman