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Molecular structure
of the luciferase gene from the dinoflagellate Pyrocystis lunula
Okamoto, O.1,
Liu, Liyun1, Robertson, D.2
and Hastings, J. Woodland1
Harvard University1
Clark University2
Abstract-
The morphology of the bioluminescent marine dinoflagellate Pyrocystis
lunula is very different from that of Lingulodinium polyedrum
(formerly Gonyaulax polyedra), and the circadian control of its
luciferase activity is also different: the protein is not synthesized
and destroyed on a daily basis. The sequence and structure of its gene
is also of interest for phylogenetic purposes. As in L. polyedrum,
the luciferase gene of P. lunula is composed of three contiguous
domains that share more than 70% intramolecular identity at both the
amino acid and nucleotide levels. In addition, the N-terminal region
that precedes the repeated domains is about 36% identical to the corresponding
regions of L. polyedrum luciferase and luciferin binding protein.
Two of the repeated P. lunula domains have been analyzed; as
in L. polyedrum, their central regions are more highly conserved
(89% at the amino acid level) than are the flanking regions. Comparative
sequence analyses among the full length domains of P. lunula
and L. polyedrum luciferases show that the degree of intermolecular
conservation of individual domains is higher than that of intramolecular
conservation between different domains. In addition, the low frequency
of synonymous codon substitutions in the central region of each domain
of L. polyedrum luciferase (relative to the flanking regions)
is not found in P. lunula. The similarity between the luciferases
of these two species suggests that the domain structure may have arisen
through a duplication event that occurred prior to the divergence of
these dinoflagellate groups.
Keywords: evolution
of luciferase, dinoflagellate, Pyrocystis lunula, luciferase
gene
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