We previously identified a gene, Mblk-1, that encodes a putative transcription factor with two DNA-binding motifs expressed preferentially in the honeybee brain [H. Takeuchi et al., Insect Mol. Biol. 10, 487-494 (2001)]. In the present study, we identified its preferred binding sequence as 5-CCCTATCGATCG-ATCTCTACCT-3' and characterized its DNA-binding properties using truncated Mblk-1 mutants. An electrophoretic mobility shift assay revealed that the full-length Mblk-1 binds to the sequence with high affinity, whereas each truncated DNA-binding motif of Mblk-1 binds with much lower affinities. An in vitro pull-down assay indicated that each DNA-binding motif affords homodimeric bindings, suggesting that Mblk-1 functions as a dimer. (C) 2002 Elsevier Science (USA).