Characterization of the proteinaceous skeletal organic matrix from the precious coralCorallium konojoi

Abstract

The Japanese red and pink corals are known to be precious because of their commercial value resulting from their use in ornaments, jewelry, and medicine. Precious corals are very interesting models for biomineralization studies and possess two different skeletal structures: an axial skeleton and an endoskeleton (sclerites). Although it has long been known that the organic matrix proteins existing in coral skeletons are critical for the oriented precipitation of CaCO3 crystals, these proteins in moderate deep-sea Japanese precious corals remain uncharacterized. Therefore, in this study, we performed skeletal whole proteome analyses using 1D and 2D electrophoresis, nano-LC, and MALDI-TOF-TOF MS. We identified a total of 147 functional coral skeletal organic matrix proteins (120 from the sclerites and 36 from the axial skeleton), including two calcium-binding calmodulin. Among the organic matrix proteins identified, nine key proteins are highly typical and common in both skeletons. Strong glycosylation activity, which is essential for skeletal formation in calcifying organisms, was detected in both skeletons. This work demonstrates unique biomineralization-related proteins in precious corals and provides the first description of the major proteinaceous components of CaCO3 minerals in precious corals, enabling the comparative investigation of biocalcification in other octocorals.

The Biomineralization Proteome: Protein Complexity for a Complex Bioceramic Assembly Process

“…The transcriptome or RNA expression levels in these organisms are also being explored with the goal of understanding the timing of transcription, translation, and protein secretion as it pertains to the events occurring in the biomineralizing matrix . What has emerged from these studies…”

“…Within these genomes lurk mineralization‐associated genes. Since many biomineral‐associated proteins are extracellular and thus subjected to post‐translational modifications, these genomic studies have been augmented by proteomic studies that identify gene products that are phosphorylated, sulfated, glycosylated, enzymatically cleaved, or otherwise chemically modified at side‐chain groups . The challenge that we are now facing is to identify these mineralization‐associated proteins, their structure, synthesis, secretion, and temporal/regional localization, and most importantly, their purpose or function.…”

An Overview of the Medical Applications of Marine Skeletal Matrix Proteins

“…Recently, we perceived protein induced crystallization [ 2 , 7 , 8 , 12 , 13 ], which showed potential crystal design and growth that could help medicinal chemistry in drug design. Our primary chemical proteomic results from soft coral revealed a number of molecules with high concentrations [ 5 , 14 ]. In addition, some proteins extracted from soft corals are homologous with many human proteins, making them useful due to their similarity [ 15 , 16 ].…”

“…Skeletal proteins and polysaccharides in marine organisms are present as complex mixtures within organic matrices. The organic matrices of marine calcifiers, for example, are a potentially untapped source of skeletal proteins [ 1 , 2 , 3 , 4 , 5 , 6 ]. Organic matrices have the advantage of being naturally produced, retaining the native, functional conformation of the original proteins.…”

“…Proteins with potential for bone repair and drug discovery, extracted either from naturally occurring skeletal organic matrices or derived from cultivated tissues, can be identified and isolated using chromatography, cell assays and proteomic methods [ 1 , 9 , 11 ]. Proteomics is a high-throughput analytical method for rapidly identifying known or unknown proteins in complex mixtures [ 5 ]. If purification methods can be established for skeletal proteins derived from calcifying marine organisms, researchers in the emerging fields of proteomics and medicinal chemistry could utilize these methods for subsequent drug discovery and, as a more specific example, bone repair.…”