DISTRIBUTION AND COMPOSITION OF MATRIX PROTEIN IN THE RADULA TEETH OF THE CHITON ACANTHOPLEURA-HIRTOSA

The organic matrix of the major lateral teeth of the chiton Acanthopleura hirtosa was found to consist of approx 10% by weight of protein. Histochemical analysis indicated that the majority of the protein was located in the calcified (anterior) region of the tooth, while the iron-mineralized or posterior region contained relatively small amounts of protein. In comparison, whole radula tissue contained significantly greater amounts of protein than the major lateral teeth alone. This extra protein is required to harden the non-mineralized areas of the radula. High-performance liquid chromatography and biochemical analyses indicated that the protein is rich in aspartic and glutamic acids, while phosphoserine was also detected in appreciable quantities. In addition, the protein component was closely associated with chitin fibres which comprise the remainder of the organic matrix. It is suggested that the calcified region of the tooth exhibits greater organic matrix-mediated control during the biomineralization process than the iron-mineralized posterior region.