Fig. 1.

A schematic representation showing the genomic structure of Ns lcf genes and the domain organization of their predicted proteins in comparison with the second domain of Lp LCF and Lp LBP. At least two copies of the Ns lcf genes are tandemly arranged in a head-to-tail fashion, each consisting of 4,360 bp. The precise boundary between the intergenic region and 5′ UTR was not precisely mapped, and together they account for 1,518 bp. The 3′ UTR of the Ns lcf is only 97 bp long, therefore, much shorter than the 3′ UTRs of lcf genes of seven photosynthetic dinoflagellates, which range from 194 to 432 bp. The largest ORF of Ns lcf predicts a protein of 914 aa with two major domains, an N-terminal luciferase-like (LCF-like) domain and a C-terminal luciferin-binding protein-like (LBP-like) domain. The LCF-like domain shares a 56% sequence identity with but is shorter at the N terminus by 60 aa residues than the individual domains of Lp LCF. The LBP-like domain of 591 aa residues is 41% identical with the comparable region of Lp LBP. No significant similarity was found between the most N-terminal sequence of 29 aa residues of the Ns LCF and any sequences in the database.