Abstract
The nature of coloration in many marine animals remains poorly investigated. Here we studied the blue pigment of a scyfoid jellyfish Rhizostoma pulmo and determined it to be a soluble extracellular 30-kDa chromoprotein with a complex absorption spectrum peaking at 420, 588, and 624 nm. Furthermore, we cloned the corresponding cDNA and confirmed its identity by immunoblotting and mass spectrometry experiments. The chromoprotein, named rpulFKz1, consists of two domains, a Frizzled cysteine-rich domain and a Kringle domain, inserted into one another. Generally, Frizzleds are members of a basic Wnt signal transduction pathway investigated intensely with regard to development and cancerogenesis. Kringles are autonomous structural domains found throughout the blood clotting and fibrinolytic proteins. Neither Frizzled and Kringle domains association with any type of coloration nor Kringle intrusion into Frizzled sequence was ever observed. Thus, rpulFKz1 represents a new class of animal pigments, whose chromogenic group remains undetermined. The striking homology between a chromoprotein and members of the signal transduction pathway provides a novel node in the evolution track of growth factor-mediated morphogenesis compounds.
Highlights
From the ‡Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya 16/10, 117997 Moscow, Russia and ¶Evrogen JSC, Miklukho-Maklaya 16/10, 117997 Moscow, Russia
We studied the blue pigment of a scyfoid jellyfish Rhizostoma pulmo and determined it to be a soluble extracellular 30-kDa chromoprotein with a complex absorption spectrum peaking at 420, 588, and 624 nm
We concluded that the blue pigment from Rhizostoma did not belong to the carotenoprotein family
Summary
New Class of Blue Animal Pigments Based on Frizzled and Kringle Protein Domains*. The nucleotide sequence(s) reported in this paper has been submitted to the GenBankTM/EBI Data Bank with accession number(s) AY507144 This fact is explained by an inevitably more complex structure of blue pigments compared to yellow-reds. Several known types of protein-based animal pigments can be distinguished: carotenoproteins (including rhodopsins, where carotenoids feature an unusual covalent bond to apoprotein), heme-, flavin-, or metal-containing proteins, pterins, melanins, ommochromes [1], and members of the green fluorescent protein (GFP) family [3]. This work revealed a new class of pigments based on a unique combination of well known Frizzled and Kringle protein domains that are tightly bound to a chromogenic group of an unknown structure
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