Nucleotide sequence of a new BALB/c mouse kappa light chain variable region gene

We report here a new BALB/c mouse kappa light chain variable regk>n(Vk) genomic DNA sequence. Genbank search showed that this Vk gene has the highest homology (63%) with a human Vk gene EV15 (1). This Vk gene was cloned from the genomic DNA library of a murine hybridoma cell line designated 33.28 (2) by using a 2.7 kb Hindm fragment of mouse germline Jk region as probe (3). In hybridoma cell line 33.28, this Vk gene has been nonfiinctionally rearranged with J4 segment due to a 2 bp deletion at the Vk/J4 junction, thus causing a shift at the translational reading frame. This gene was transcribed and identified originating from the antibody producing cell of BALB/c mouse by Northern blot analysis using a 2.3 kb HindHI fragment containing this whole Vk gene as probe (data not shown). The result was confirmed by additional Northern blot analysis using a 20 bp oligonucleotide probe derived from CDR2 of this Vk gene (data not shown). Based on the nucleotide deduced amino acid sequence similarity from the amino terminus to the first invariant tryptophan, this Vk gene should be classified to Vk20 trp35 sequence group (4, 5). However, based on the number of amino acid residues from the amino terminus to the first invarient tryptophan, this Vk gene belongs to 35 aa size group while the only member of the Vk20 trp35 sequence group reported so far, MOPC265 myeloma kappa light chain belongs to 33 aa size group (4, 5). NBRF protein database search further confirmed that this Vk gene is the first member of Vk20 trp35 sequence group which does not belong to 33 aa size group.