A tentative amino acid sequence has been determined for the light chain of a mouse A-myeloma (MOPC-315) protein with anti-2,4-dinitrophenyl activity. An unusual amino acid sequence in the carboxyl-terminal 104 residues suggests that the chain represents a new class of immunoglobulin light chain. The "variable" segment of this chain (amino-terminal 110 residues) differs at only eight positions from the corresponding segment of the lambda chain of a mouse M-myeloma (MOPC-104) protein with anti-dextran activity.The recent finding of myeloma proteins with antibody activity (e.g., 1-3) and the development of procedures for the preparation of conventional antibodies of remarkably restricted heterogeneity (4, 5) provide opportunities to correlate the primary structure of immunoglobulins and their specific reactivities with particular haptens and antigens. Accordingly, we are studying the structure of protein 315, an A-myeloma protein that binds 2,4-dinitrophenyl (Dnp) ligands with high specificity (6). In this paper, we present a tentative amino acid sequence for the light chain (LI5) of this protein. An unusual sequence suggests that this chain represents a new type, resembling immunoglobulin light chains of the X type more than those of the K type.Protein 315 was isolated from sera of mice bearing tranisplants of MOPC-315, a plasma cell tumor*, whose origin is described below. Fully reduced carboxymethylated or aminoethylated light chains were prepared as described (40), and digested with trypsin, thermolysin, or pepsin. The peptides were purified by ion-exchange chromatography on Dowex resins (7) or SE-Sephadex (8), and their amino acid sequences were determined by Edman degradation (9). The successively removed amino-terminal residues were identified by: subtractive analysis, gas-liquid chromatography of CH3CNS amino acids (9), the dansyl procedure (10) G-100 in 5 M guanidine -HCl, followed by chromatography on CM-cellulose in 8 M urea (11). Antisera to LI'' were prepared by immunizing rabbits with the Fab fragment of protein 315 in complete Freund's adjuvant, and absorbing the sera with K-and X-containing A-myeloma proteins that were produced by plasma cell tumors MOPC-460 and S-176*.A complete set of peptides was not isolated from any one enzymatic digest, but a combination of peptides from trypsin and thermolysin digests accounted for the amino acid composition of the chain (Table 1), and provided the basis for the provisional sequence shown in Fig. 1. As few overlaps have been established thus far, the alignment of peptides was based largely on homology with the complete amino acid sequence of the mouse X light chain that is produced by plasma cell tumor MOPC-104 (12); this light chain is hereafter referred to as L104. There are two methionine residues in L315, and the three purified cyanogen bromide fragments obtained from this chain (corresponding to the N-terminal 87 residues, the central 88 residues, and the C-terminal 39
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.