Abstract
Stony corals generate their calcium carbonate exoskeleton in a highly controlled biomineralization process mediated by a variety of macromolecules including proteins. Fully identifying and classifying these proteins is crucial to understanding their role in exoskeleton formation, yet no optimal method to purify and characterize the full suite of extracted coral skeletal proteins has been established and hence their complete composition remains obscure. Here, we tested four skeletal protein purification protocols using acetone precipitation and ultrafiltration dialysis filters to present a comprehensive scleractinian coral skeletal proteome. We identified a total of 60 proteins in the coral skeleton, 44 of which were not present in previously published stony coral skeletal proteomes. Extracted protein purification protocols carried out in this study revealed that no one method captures all proteins and each protocol revealed a unique set of method-exclusive proteins. To better understand the general mechanism of skeletal protein transportation, we further examined the proteins’ gene ontology, transmembrane domains, and signal peptides. We found that transmembrane domain proteins and signal peptide secretion pathways, by themselves, could not explain the transportation of proteins to the skeleton. We therefore propose that some proteins are transported to the skeleton via non-traditional secretion pathways.
Highlights
Scleractinian corals, or stony corals, are the most prolific biomineralizers in phylum Cnidaria [1]
8.3% of the proteins overlapped between methods while 78.3% and 13.3% of the proteins were exclusive to combined centrifugation ultrafiltration filters (CF) and combined acetone precipitation (ACT) fraction data, respectively
When preparing coral skeletal proteomes, we propose that a multi-method approach to cleaning, demineralization, and protein purification should be used
Summary
Scleractinian corals, or stony corals, are the most prolific biomineralizers in phylum Cnidaria [1] They are a key component of shallow-water tropical reefs, often forming massive structures that serve as the foundation of an ecosystem which hosts some of the more biodiverse communities on the planet [2, 3]. They are amongst the oldest biomineralizing metazoans, producing calcium carbonate (CaCO3) exoskeletons in the form of aragonite through biologically-directed mechanisms [4, 5], which. The SOM consists of proteins, lipids, and polysaccharides, which are not present in the abiotic
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