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Updated: Aug 24, 2026

Physiological Experimentation with the Crayfish Hindgut: A Student Laboratory Exercise
Published on: January 18, 2011
A novel calcium-binding peptide from the cuticle of the crayfish, Procambarus clarkii
Hirotaka Inoue1, Tsuyoshi Ohira, Noriaki Ozaki
1Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo, Tokyo 113-8657, Japan. aa27009@mail.ecc.u-tokyo.ac.jp
Abstract:
A novel peptide named calcification-associated peptide (CAP)-2 was isolated from the exoskeleton of the crayfish, Procambarus clarkii. CAP-2 consists of 65 amino acid residues and has a 44% sequence identity with CAP-1 characterized previously. It has a chitin-binding domain observed in many arthropod cuticle proteins. CAP-2 showed inhibitory activity on calcium carbonate precipitation and chitin-binding ability. A CAP-2 cDNA was cloned using RT-PCR and RACE and the open reading frame encoded a precursor peptide consisting of a signal peptide and CAP-2. RT-PCR revealed that CAP-2 mRNA was exclusively expressed in the epidermal tissue during the postmolt stage, the site and stage being associated with calcification. Calcium-binding assay using recombinant CAP-2 revealed that this peptide had affinity for calcium ions with a Kd value of about 1 mM. All these results suggest that CAP-2 serves as a nucleator or a regulator in the calcification of the exoskeleton.
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