An Overview of the Medical Applications of Marine Skeletal Matrix Proteins

Abstract

In recent years, the medicinal potential of marine organisms has attracted increasing attention. This is due to their immense diversity and adaptation to unique ecological niches that has led to vast physiological and biochemical diversification. Among these organisms, marine calcifiers are an abundant source of novel proteins and chemical entities that can be used for drug discovery. Studies of the skeletal organic matrix proteins of marine calcifiers have focused on biomedical applications such as the identification of growth inducing proteins that can be used for bone regeneration, for example, 2/4 bone morphogenic proteins (BMP). Although a few reports on the functions of proteins derived from marine calcifiers can be found in the literature, marine calcifiers themselves remain an untapped source of proteins for the development of innovative pharmaceuticals. Following an overview of the current knowledge of skeletal organic matrix proteins from marine calcifiers, this review will focus on various aspects of marine skeletal protein research including sources, biosynthesis, structures, and possible strategies for chemical or physical modification. Special attention will be given to potential medical applications and recent discoveries of skeletal proteins and polysaccharides with biologically appealing characteristics. In addition, I will introduce an effective protocol for sample preparation and protein purification that includes isolation technology for biopolymers (of both soluble and insoluble organic matrices) from coralline algae. These algae are a widespread but poorly studied group of shallow marine calcifiers that have great potential for marine drug discovery.

Keywords: biomineralization; chitin; collagen; coralline algae; marine calcifiers; marine skeletal proteins; proteomics.

Figure 1

Identification of chitin and collagen in algal skeletal protein-polysaccharides complexes. Structural comparison of FTIR spectra between organic matrix fractions (soluble organic matrix (SOM) and insoluble organic matrix (IOM)) and bulk skeletal powder. Graphs for SOM, IOM fractions and bulk skeletal powder are indicated. Different colored boxes in the spectra indicate involvement of molecules in SOM and IOM fractions in forming skeletal structure in coralline algal calcification system. (Reproduced from Scientific Reports, Rahman and Halfar 2014 [7]).

Figure 2

Model of general strategy for analyzing protein-polysaccharides complex from skeletal organic matrix of marine calcifiers.

Figure 3

Electrophoretic analysis of skeletal matrix proteins extracted from the coralline red alga C. compactum. (A) SDS-PAGE fractionation with Coomassie Brilliant Blue (CBB) staining after purification of the skeletal proteins. Lane 1 and 2 indicate purified skeletal proteins. Arrows indicate protein bands; (B) SDS-PAGE gel with Periodic Acid-Schiff (PAS) staining to identify glycoprotein in skeletal matrix proteins of C. compactum. Lane 1 and 2, a strong abundant chitin associated glycoprotein was identified (indicated by arrow) by periodic Acid-Schiff staining. An eluate (derived from 5 g of algal skeleton) was run on 12% polyacrylamide gel M, protein marker. The Precision Plus SDS-PAGE standard (Bio-Rad) was used as protein marker for electrophoresis.