Continued Production of a Single Light Chain Population of Rabbit Antibody during Repeated Immunization: Amino Acid Composition and Sequence

Abstract

Abstract In previous reports, anti-p-azobenzoate antibody produced by a single rabbit for a period of about a year was shown by specific fractionation to consist of principally two molecular species for the first half year after which production of one of the species apparently ceased while production of the other species persisted for at least another half year. Comparative studies were undertaken of the amino acid compositions and the amino-terminal amino acid sequences at the first 11 positions of the light chains from an antibody fraction (BE-1) containing both antibodies and from a fraction (BE-3) containing only one of the antibodies. The amino acid compositions of BE-1 and BE-3 light chains are almost the same except for probable small differences in histidine, aspartic acid and tyrosine. Light chain BE-3, previously shown to give a single band on disc-electrophoresis, also gave a single amino-terminal amino acid sequence, Ala-Val-Leu-Thr-Glx-Thr-Pro-Ser-Ser-Ser-Ser, while light chain BE-1 which showed two bands on disc electrophoresis, showed the amino-terminal amino acid sequence, . At position 5, glutamine (or glutamic acid) and threonine were found in almost equal quantities. The residue at position 6 was not identified unambiguously. Since one of two bands of BE-1 light chain correspond to BE-3 light chain, the other band (slow-moving band) has the amino-terminal amino acid sequence Ala-Val-Leu-Thr-Thr-Thr-( )-Ser-Ser-Ser-Ser. Thus rabbit No. 2663 produced two closely related antibody light chains and one of them disappeared in the latter half of the year. The present sequences are compared with other reported sequences of anti-carbohydrate and anti-azobenzoate antibody light chains. The present amino acid sequence studies were carried out by a modified manual Edman degradation.